Need a field to enter General description on the invoice

We have requriment from user that they want to enter some addditional information( Genereal description about the invoice) on the invoice and print. They want to enter this information for all invoices.

we have already using "Transaction Information" and "Invoice Transacion Flexfield" so we cannot use with these dff with different context too.

We have already using comments field(In more Tab) and Memo field (In Notes tab) for some other information to enter and print on the invoice.

So please help me if you had impletemented any thing else to capture the information and print the information.

Thanks,

Thanoj Kumar