Generating Cover Eligibility Group

Dear Gurus,

I have a request to create a group of cover groups. The cover group should be derived from budget data i.e. Fund, funds centre and Commitment Item.

In the budget data entered through FMBB, the combination will be a single fund, fund centre and multiple commitmnt items.

How can I set up the derivation (FMCERG)to get the data from the budget data per fund/fund centre and multiple commitment items(FMCEGENCG)into a single cover group?

Thanks