SLA rule to combine capital and non-capital cost

Summary

Client has both capital and no capital (billable/expense) cost on a capital project. I need to create a SLA rule to combine this. Capital cost are based on Task DFF and non capital cost are in mapping

Content

Client has capital cost and non capital cost on a capital project. As I can't assign separate rule for capital cost and other cost, I have to combine my accounting logic in a single account rule. Capital cost are derived from a Task DFF. In the task DFF I maintain the asset category which in a separate value set is mapped to a GL account (in the description). For non capital cost I use a mapping set, mapping the expenditure type to the GL account. For both cost types (capital and non-capital) I can create separate account rules, but when