Writeable ListBox?

It was brought to my attention that I maybe able to accomplish my task by including a seperate textbox with the same name as the listbox that way if the user doesn't see what he needs in the listbox then they can add an entry in the textbox. Can this be done? I have attempted to code the controls as follows however, name is not a property of asp:textbox: My insert code is based on the 'id' indentifier. How can I get this to work or will it? Thank you for your thoughts. Sincerely, Tim