Reconcillation account to be filled based on Account group and Company code

Hi Experts,

               I have the following requirement in MDG.

I want to automatically populate reconcillation account field on the basis of account group and company code.

  I used BADI USMD_RULE_SERVICE. In this I created by implementation. In this implementation i have put entity type BP_COMPANY for model BP.

The problem is when i check Derive_entity method i get company code and reconcillation field but didn't get account group. Can some one please help how to acheive it as i am not  much aware of MDG.

Thanks & Regards

Pawan Rai