Extern "User32" fails

I wanted to use Extern "user32" so that I could access some API functions such as GetWindowLong, SetWindowLong, ShowWindow etc but the compiler says "Unrecognised calling convention 'User32'".

In fact the reason I want these is so that if I create a graphics window using depth 0 I can add minimise/maximise and close buttons (inc. System Menu) with API calls. Unless there is an easier way, is there?

here are a few dll calls, the "win32"is the calling convention , not the dll:

Extern "win32"
	Function SetWindowPos:Int(hWnd,hWndInsertAfter,x,y,cx,cy,wFlags) = "SetWindowPos@28"
	Function GetWindowLong :Int(hWnd ,nIndex)= "GetWindowLongA@8"
	Function GetActiveWindow:Int()= "GetActiveWindow@0"
	Function SetWindowLong :Int(hWnd ,nIndex,lNewLong )= "SetWindowLongA@12"	
End Extern

Great, thanks for that!