My I'm being rather helpful today..
d3d7graphics.bmx : Line 79
And the MSDN page : http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/createwindowex.asp
d3d7graphics.bmx : Line 79
hwnd=CreateWindowExA( 0,DX_CLASS_NAME,wndTitle,style,CW_USEDEFAULT,CW_USEDEFAULT,width,height,0,0,hinst,Null )
And the MSDN page : http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/windowing/windows/windowreference/windowfunctions/createwindowex.asp