Hi,
It it is not possible to assign AVC constrol without assigning activity group or all groups. This field is required.
But in the activity derivation strategy there is no standard value type, which is describe Return or Transfer posting for budet correction (via FMBB).
http://help.sap.com/saphelp_erp2004/helpdata/en/b7/d85598576c11d295960000e835339d/content.htm
AVC control perfectly work during actual postings in FI and for example
during FMWA transaction run, but don't work during FMBB.
Probably I miss something else.
BR,
Kristina