Grouping customers and view customer open items list - Group wise

Hi.

I have some requirement from my client.

He says that he want to view customer open items list group wise.

In FBL5N we can give the selection of multiple customers. But he wants to group the specific customers and then view the open items for this group.

For example: Client has 10 customers and out of these customers he wants to select and group 5 customers. And then he want to view open items list for this group.

Can anyone help me how to group these specific customers in the total customers list. Also request you to provide me the option to view open items for this group of customers.

Regards,

Padmavathi