Sounds like what you are looking for is National Accounts. Unfortunately this does not yet exist for Adagio.

The ACCPAC Plus version of this module consolidates all invoices for selected customers into one account. For example if you had individual accounts for every Sears store but got one cheque from head office then National Accounts could be used to consolidate all Sears invoices for cash receipts processing.

Another option would be to have a custom cash receipt process created that would allow you to enter receipts by invoice number.