Add Comments field to Cash Receipts Entry > A\R Receipt > Allocate tab Invoices Grid

Our Accounting Dept wants to be able to add a standard ‘reason comment’ to Cash Receipts to indicate why a partial payment was made.
How can I add the erp.CashDtl.Comment field to the Cash Receipts Entry > A\R Receipt > Allocate tab Invoices Grid? Can I add a dropdown of standard comments to the field or would I use a UD field for this?

Doreen - Did you figure out how to do this? Our Accounting Dept is asking if there is a comment/notes field that could be entered when “On Account” is checked that would carry over to the Credit Memo that is auto created. Would be interested if you were able to add a comment field to the Allocate tab.
Thanks,
Debbie