Check if external program is finished

How do i check when an externally run program is finished? I have a button menu which launches programs, I want the button menu to disappear after an external program is selected, then reappear when that external program is closed.

Thanks.

I though I resolved it with:

VB Code:

System.Diagnostics.Process.Start(<[i]external prog here[/i]>).WaitForExit()

but after a short while, the menu pops back up in front of the external program it's running, does anyone know why? or how to properly check if a program's ended?