Add form to select items - repost

I have an already existing excel sheet, but I need some work done on it. When you click on the account name in column D a pop up appears and you can select an account. I would like to add another form to the pop up. I want it to appear at the top of the current form. It would be laid out the same as the current form, but the form would be populated with account descriptions and account numbers that have already been selected and that are existing in column D.