Maybe it was Data|Validation.

Debra Dalgleish has tons of tips and hints at:
http://www.contextures.com/xlDataVal01.html

szeng wrote:

I want to setup a workbook that for cell 1 in sheet 1, it would be shown as
an edit combox-like cell, and its value would be associated with an range
values defined (as a defined name) in sheet 2. So when I click on cell 1, a
drop-down list would show all the values in that defined name. I would then
be able to select one of the values. I saw one sample workbook has such an
edit combox-like cell but cannot figure out how it was done. I checked into
Visual Basic Editor and didn't find any macro codes defined anywhere in that
workbook. Any suggestion?

--

Dave Peterson