Add field for account move line different than description

We've seen that when we make a quotation, the field "Ref. Client" becomes in the invoice the field "Description" and becomes in the account move line the field "Name". this field name is finally displayed in the account journal. People from the accounting department said that the original value of the field (the one in the quotation) is really not necessary in the account journal. For example, if we write in the invoice Ref client : your call from 10.10.2009, this text will be the same in the account journal which has, for the accounting, no information. So, the idea, when creating the invoice, is a new field whith a value that is really necessary for the accounting department. This value could proposed by merging the partner client name and the invoice number and should be editable.
This is a really need for them .
Thanks