Hi Anil,
By SAP standard functionality, you can only assign a single planning group to a vendor, which would default into each open AP invoice document.
From what I can see as highlevel possible solution you could achieve the client requirement by implementing either user exit or business transaction event to manipulate the assignment of planning group on line item level (BSEG-FDLEV) based on your specific criteria.
I once used a Business Transaction Event to achieve some similar requirement.
hope that this helps
Taro