ALE Distribution Question

We have a scenario triggering MATMAS Idocs to other systems.

Change pointers activated.

So Matmas Sent from system A to B and A to C.

in System B then can change some thing which comes back to A as Inbound Idoc and will be posted to System A.

this triggers MAtMAS again sending data from A to B.

Its like a Loop.. right ?

How can u avoid those situations?. I just want to add new field to BD64 model so that If a change made by particular User should not be triggered Change pointers.

Can someone explain me how that works. In BD 64 there are not many fields in MATMAS you can select to filter out.

Please help.