Hi,
You have two options:
a) work with budget structure and derive budget address, either by creating a rule for each line or making more sophisticated rule reading superior commitment item from master data of posting CI
b) work with control objects in AVC. The concept is more or less the same as with budgetary structure
Regards,
Eli
P.S. FMDERIVE suggested by Yasin is a bit problematic: it would not only consume the budget on the superior CI, but also post on it. I.e. you will loose in your FM history the original FM assignment. Normally, this comes against with client's requirements. That's why there is a solution of budget structure and/or AVC control objects
P.P.S. ... and a small advertisement. If you want to see how things are working for FM configuration, you can consult this blog Configuring Funds Management: New E-Bite by SAP Press