IDOC from One System to another

Hi All,

I am sending idocs from one system to another For Eg System A to System B .

Now suppose 2 idocs are generated 1 and 2.

Now how to determine , for idoc 1 in system A, what is the corresponding Inbound Idoc in System B because the data which is coming in System B might be different than in System A for the same Idoc?

Thanks in Advance.