Cost center and GL account restriction in Purchase order

Hi Friends,

While creating a Purchase order we enter the GL account and the cost center. Normally we can change this cost center and we can choose any otherone. Here our requirement is, we want to restrict this GL account and cost center combination. For example one GL account should be allowed to take two cost centers A and B only not more than that. I hope in FICO module we can fulfil such requirements through validation rules and i am not able find any workaround in MM mdoule to figure out this issues. Could you please help me on this

Thanks for your help.

Kanna