Dropdown Box Update
 

I am trying to update a spreadsheet that was developed a few years ago (not
sure what version of Excel it was created in). I am using Excel 2003. The
spreadsheet has a dropdown that I need to include more values in. However, I
am unable to update the dropdown values through using data validation or the
form controls toolbar. Also, it doesn't look like a normal data validation
dropdown in that the dropdown box only uses part of the cell it occupies and
just has a different look to it.

Any thoughts?