I just noticed that the ActivateApp statement feels ok even if the given window name is not exactly what the window title it.
' if you have multiple windows then just provide a unique name ' within the first 6 letters in this example ActivateApp Left$(me.myWindowName, 6)
Ok, that's documented in the help of Domino Designer, but it really works. So if you experience problems with that statement when providing the full window title just try to shorten it.
I experienced problems with ActivateApp sometimes ("Illegal function call") so I ran into this issue and the solution.