I have a question about creating a Feeder for the following cube:

I understood the Feeder-logic works like this: Look in Cell "Mes1". If there is a non-zero Value in the cell Flag the corresponding cell in "Mes3" so that TM1 can use this value for the consolidation (The Rule gonne be calculated anyways).
The example above behaves like I expacted.
But how would you write the correct feeder which also flags the 0-value?
Any ideas?