I was using this to test GPOs were run at user login. if the popup displayed then i knew the object had been executed.
START CMD /C "ECHO Popup Test && PAUSE"
vbs (will call and execute the exe from the specified location):
Set wshShell = WScript.CreateObject ("WSCript.shell")
wshshell.run "%userprofile%\desktop\popup-test.exe", 6, True
set wshshell = nothing