Index: rts/Game/UI/GuiHandler.cpp
===================================================================
--- rts/Game/UI/GuiHandler.cpp	(revision 1451)
+++ rts/Game/UI/GuiHandler.cpp	(working copy)
@@ -32,6 +32,7 @@
 #include "SDL_keysym.h"
 #include "SDL_mouse.h"
 #include "mmgr.h"
+#include "Sim/Units/CommandAI/CommandAI.h"
 
 //////////////////////////////////////////////////////////////////////
 // Construction/Destruction
@@ -1304,9 +1305,31 @@
 	CUnit* unit=0;
 	float dist2=helper->GuiTraceRay(camera->pos,mouse->dir,gu->viewRange*1.4,unit,20,true);
 
-	if(unit && keys[SDLK_LSHIFT] && keys[SDLK_LCTRL]){		//circle build around building
-		UnitDef* unitdef2=unit->unitDef;
-		float3 pos2=unit->pos;
+	UnitDef* unitdef2=0;
+	float3 buildPos;
+	if(unit){
+		unitdef2=unit->unitDef;
+		buildPos = unit->pos;
+	} else if(keys[SDLK_LSHIFT] && keys[SDLK_LCTRL]){
+		Command c = uh->GetBuildCommand(camera->pos,mouse->dir);
+		if(c.id < 0){
+			unitdef2=unitDefHandler->GetUnitByID(-c.id);
+			buildPos.x = c.params[0];
+			buildPos.y = c.params[1];
+			buildPos.z = c.params[2];
+		}
+	}
+
+
+
+	if(unitdef2 && keys[SDLK_LSHIFT] && keys[SDLK_LCTRL]){		//circle build around building
+		Command c;
+		c.id = -unitdef->id;
+		c.params.push_back(0);
+		c.params.push_back(0);
+		c.params.push_back(0);
+
+		float3 pos2 = buildPos;
 		pos2=helper->Pos2BuildPos(pos2,unitdef2);
 		start=pos2;
 		end=pos2;
@@ -1321,7 +1344,19 @@
 			p2.x+=(unitdef->xsize/2)*SQUARE_SIZE;
 			p2.z-=(unitdef->ysize/2)*SQUARE_SIZE;
 			p2=helper->Pos2BuildPos(p2,unitdef);
-			ret.push_back(p2);
+			c.params[0] = p2.x;
+			c.params[1] = p2.y;
+			c.params[2] = p2.z;
+			bool cancel = false;
+			std::set<CUnit*>::iterator ui = selectedUnits.selectedUnits.begin();
+			for(;ui != selectedUnits.selectedUnits.end() && !cancel; ++ui){
+				if((*ui)->commandAI->WillCancelQueued(c)){
+					cancel = true;
+				}
+			}
+			if(!cancel){
+				ret.push_back(p2);
+			}
 		}
 		pos=start;
 		pos.x=end.x;
@@ -1330,7 +1365,19 @@
 			p2.x+=(unitdef->xsize/2)*SQUARE_SIZE;
 			p2.z+=(unitdef->ysize/2)*SQUARE_SIZE;
 			p2=helper->Pos2BuildPos(p2,unitdef);
-			ret.push_back(p2);
+			c.params[0] = p2.x;
+			c.params[1] = p2.y;
+			c.params[2] = p2.z;
+			bool cancel = false;
+			std::set<CUnit*>::iterator ui = selectedUnits.selectedUnits.begin();
+			for(;ui != selectedUnits.selectedUnits.end() && !cancel; ++ui){
+				if((*ui)->commandAI->WillCancelQueued(c)){
+					cancel = true;
+				}
+			}
+			if(!cancel){
+				ret.push_back(p2);
+			}
 		}
 		pos=end;
 		for(;pos.x>=start.x;pos.x-=unitdef->xsize*SQUARE_SIZE){
@@ -1338,7 +1385,19 @@
 			p2.x-=(unitdef->xsize/2)*SQUARE_SIZE;
 			p2.z+=(unitdef->ysize/2)*SQUARE_SIZE;
 			p2=helper->Pos2BuildPos(p2,unitdef);
-			ret.push_back(p2);
+			c.params[0] = p2.x;
+			c.params[1] = p2.y;
+			c.params[2] = p2.z;
+			bool cancel = false;
+			std::set<CUnit*>::iterator ui = selectedUnits.selectedUnits.begin();
+			for(;ui != selectedUnits.selectedUnits.end() && !cancel; ++ui){
+				if((*ui)->commandAI->WillCancelQueued(c)){
+					cancel = true;
+				}
+			}
+			if(!cancel){
+				ret.push_back(p2);
+			}
 		}
 		pos=end;
 		pos.x=start.x;
@@ -1347,7 +1406,19 @@
 			p2.x-=(unitdef->xsize/2)*SQUARE_SIZE;
 			p2.z-=(unitdef->ysize/2)*SQUARE_SIZE;
 			p2=helper->Pos2BuildPos(p2,unitdef);
-			ret.push_back(p2);
+			c.params[0] = p2.x;
+			c.params[1] = p2.y;
+			c.params[2] = p2.z;
+			bool cancel = false;
+			std::set<CUnit*>::iterator ui = selectedUnits.selectedUnits.begin();
+			for(;ui != selectedUnits.selectedUnits.end() && !cancel; ++ui){
+				if((*ui)->commandAI->WillCancelQueued(c)){
+					cancel = true;
+				}
+			}
+			if(!cancel){
+				ret.push_back(p2);
+			}
 		}
 	} else if(keys[SDLK_LALT]){			//build a rectangle
 		float xsize=unitdef->xsize*8+buildSpacing*16;
Index: rts/Sim/Units/CommandAI/CommandAI.cpp
===================================================================
--- rts/Sim/Units/CommandAI/CommandAI.cpp	(revision 1451)
+++ rts/Sim/Units/CommandAI/CommandAI.cpp	(working copy)
@@ -349,6 +349,33 @@
 		SlowUpdate();
 }
 
+/**
+* @brief Determins if c will cancel a queued command
+* @return true if c will cancel a queued command
+**/
+bool CCommandAI::WillCancelQueued(Command &c)
+{
+	if(!commandQue.empty()){
+		std::deque<Command>::iterator ci=commandQue.end();
+		for(--ci;ci!=commandQue.begin();--ci){							//iterate from the end and dont check the current order
+			if((ci->id==c.id || (c.id<0 && ci->id<0)) && ci->params.size()==c.params.size()){
+				if(c.params.size()==1){			//we assume the param is a unit of feature id
+					if(ci->params[0]==c.params[0]){
+						return true;
+					}
+				} else if(c.params.size()>=3){		//we assume this means that the first 3 makes a position
+					float3 cpos(c.params[0],c.params[1],c.params[2]);
+					float3 cipos(ci->params[0],ci->params[1],ci->params[2]);
+					if((cpos-cipos).SqLength2D()<17*17){
+						return true;
+					}
+				}
+			}
+		}
+	}
+	return false;
+}
+
 void CCommandAI::SlowUpdate()
 {
 	if(commandQue.empty())
Index: rts/Sim/Units/CommandAI/CommandAI.h
===================================================================
--- rts/Sim/Units/CommandAI/CommandAI.h	(revision 1451)
+++ rts/Sim/Units/CommandAI/CommandAI.h	(working copy)
@@ -29,6 +29,7 @@
 	virtual void WeaponFired(CWeapon* weapon);
 	virtual void BuggerOff(float3 pos, float radius);
 	virtual void LoadSave(CLoadSaveInterface* file, bool loading);
+	virtual bool WillCancelQueued(Command &c);
 
 	void AddStockpileWeapon(CWeapon* weapon);
 	void StockpileChanged(CWeapon* weapon);
Index: rts/Sim/Units/UnitHandler.cpp
===================================================================
--- rts/Sim/Units/UnitHandler.cpp	(revision 1451)
+++ rts/Sim/Units/UnitHandler.cpp	(working copy)
@@ -25,6 +25,7 @@
 #include "UnitLoader.h"
 #include "SyncTracer.h"
 #include "Game/GameSetup.h"
+#include "Game/Command.h"
 #include "Sim/Misc/AirBaseHandler.h"
 #include "mmgr.h"
 
@@ -495,3 +496,36 @@
 	}
 	return true;
 }
+
+/**
+* returns a build Command that intersects the ray described by pos and dir from the command queues of the
+* units units on team number team
+* @breif returns a build Command that intersects the ray described by pos and dir
+* @return the build Command, or 0 if one is not found
+*/
+
+Command CUnitHandler::GetBuildCommand(float3 pos, float3 dir){
+	float3 tempF1 = pos;
+	std::list<CUnit*>::iterator ui = this->activeUnits.begin();
+	std::deque<Command>::iterator ci;
+	for(; ui != this->activeUnits.end(); ui++){
+		if((*ui)->team == gu->myTeam){
+			ci = (*ui)->commandAI->commandQue.begin();
+			for(; ci != (*ui)->commandAI->commandQue.end(); ci++){
+				if((*ci).id < 0 && (*ci).params.size() >= 3){
+					tempF1.x = (*ci).params[0];
+					tempF1.y = (*ci).params[1];
+					tempF1.z = (*ci).params[2];
+					tempF1 = pos + dir*((tempF1.y - pos.y)/dir.y) - tempF1;
+					UnitDef* ud = unitDefHandler->GetUnitByID(-(*ci).id);
+					if(ud && ud->xsize/2*SQUARE_SIZE > abs(tempF1.x) && ud->ysize/2*SQUARE_SIZE > abs(tempF1.z)){
+						return (*ci);
+					}
+				}
+			}
+		}
+	}
+	Command c;
+	c.id = 0;
+	return c;
+}
Index: rts/Sim/Units/UnitHandler.h
===================================================================
--- rts/Sim/Units/UnitHandler.h	(revision 1451)
+++ rts/Sim/Units/UnitHandler.h	(working copy)
@@ -14,6 +14,7 @@
 #include <string>
 
 #include "UnitDef.h"
+#include "Game\Command.h"
 
 class CBuilderCAI;
 class CFeature;
@@ -58,6 +59,7 @@
 	float GetBuildHeight(float3 pos, const UnitDef* unitdef);
 
 	void LoadSaveUnits(CLoadSaveInterface* file, bool loading);
+	Command GetBuildCommand(float3 pos, float3 dir);
 
 	std::list<CUnit*> activeUnits;				//used to get all active units
 	std::deque<int> freeIDs;