Reg. user assigned to multiple positions in SRM org structure

Hi SRM Gurus,

We are on SRM 7.0 EHP1 classic scenario and there is a requirement to assign approvers and Buyers to multiple positions acorss various departments in the SRM organizational structure.Is this possible?? and supported in SRM.??

Because when we try to setup in organizational structure theBRF  approval workflow is not getting determined.

Any pointers are highly appreciated.

Thanks

Ankur