One of the solutions could be with a timer checking for existence of the Window with specified title, like "Acrobat Reader - [car.pdf]" as it appears when file car.pdf is open.

DECLARE INTEGER FindWindow ; 
	IN WIN32API ; 
	STRING cNULL, ; 
	STRING cWinName 
lctitletext="Acrobat Reader - [car.pdf]" 
?FindWindow(0, @lctitletext)

>I use the shellexecute class to open pdf files of drawings. Is there a way to tell when the file that shellexecute opens is closed?