release strategies for purchase requisitions

Hello,

I'm having trouble with profiles and roles for release strategies, this is the scenario:

-for purchase requisitions we have two approval levels, release code S1 and S2. When release code S1 is cleared, then S2 must be approved. The head of a certain purchasing group will use S1 to approve the requisitions from his own department, and then the financial director will approve with S2. However, finance is also a purchasing group, so in some instances the finance director will have to approve with S1 and then S2.

My question is: how can we use profiles and roles so that the finance director has access with S2 to all (*) purchasing groups, but with S1 for only a certain purchasing group (in this case "500")? we can't seem to be able to define certain purchasing groups to different release codes, purchasing groups must be defined at purchsing requisitiom level.

Many thanks

Daniel