substitution when having Functional Area and target is Business Area
We are using Funds Management, and we have Functional Area field as required in all postings to FI. And we want to use Business Area functionality which would be higher level assignement than Functional Area, i.e. several Functional Areas will inculde into one Business Area, so we need to define substitution for accounting (FI) documents and substitute Business Area when prerequisite is combination of particular Functional Area and particular G/L account. But I can't find where such combination of assignements would be available in substitution rules definition.
Please help me how to define substitution when we have Functional Area and our target is Business Area?