Matt,

What it sounds like you're looking at is the result of Data Validation.
Take a look here for an explanation of how it works:

http://www.contextures.com/xlDataVal01.html

John

Matt wrote:

I have received a worksheet that seems to have hidden
combo boxes that I would like to edit. The dropdown arrow
does not appear until you select the cell and when I right
click on the arrow, the menu that appears is for a regular
cell rather than a control. I have tried to edit the
properties in design mode, but have had no luck.
Thanks for your help,
Matt