Put this in the Declarations (module):

Public Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
(ByVal lpClassName As String, ByVal lpWindowName As String) As Long

---------------------------------------

1. First find out the class name of your APP (for notepad it's "Notepad")
2. Repeat for the Other App.
(If you want to knwo how to find out the class name jsut ask)
3. Then you should put in a timer:
If (FindWindow(ClassName,Caption\Title of the app) = 0 then
.. 'Re-open your app or notify user ..
End If

Hope that is clear.

Thanx,
Mikelo2k