Call stack counter
INPUT; BINARY(4) A number identifying the location in the call stack of the call stack entry from whose message queue the messages are to be received. The number is relative to the call stack entry identified by the Call stack entry parameter. It indicates how many calls up the call stack the target entry is from the one identified by the Call stack entry parameter. Valid values follow:
0Receive the message from the message queue of the call stack entry specified in the Call stack entry parameter.
1Receive the message from the message queue of the call stack entry that is one earlier than the entry identified by the Call stack entry parameter.
n (any positive number)Receive the message from the message queue of the nth call stack entry up the stack from the call stack entry specified in the Call stack entry parameter. You can use any positive number that does not exceed the actual number of call stack entries in the call stack, excluding the external message queue.

0 = Du versucht die Nachricht deiner eigenen Aufrufebene zu lesen
1 = Die Ebene darüber
2 = die nächste Ebene
n = die n. Ebene

Du musst also nur die richtige Ebene identifizieren.