You can't control the data validation list width -- it's controlled by
the column width. You can use programming to make the column temporarily
wider. There's sample code he

http://www.contextures.com/xlDataVal08.html#Wider


yep wrote:
Can anyone show me how to change the size of a drop down list in a cell
validation? I have a number of cells next to each other, but in clicking the
drop down list for the first cell for example, the list width is not going
over the adjacent cell and thereby not showing sufficient content. I cannot
increase the cell width, otherwise my problem was solved.


--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html