Here's a procedure that waits for the user to press F4. If WaitEvent times out before a PF4 is pressed, an error is returned and the error handler kicks in:
Sub WaitForF4 ()
Dim eventF4 As Integer
With Session
On Error Goto Handler
.DefineEvent 1, rcTerminalKeystroke, "", "", 1, 1, rcIbmPf4Key
eventF4 = .WaitEvent("0:0:10")
MsgBox "Event = " & eventF4
End With
Exit Sub
Handler:
MsgBox "The F4 keystroke was not pressed."
Exit Sub
End Sub