If the other workbook is open, you can use the technique described he

http://www.contextures.com/xlDataVal05.html

Pieman wrote:
Hi, does anyone know how to create a dropdown box that will list the contents
of a column in another workbook?

Basically, I have two workbooks. One is a sales register that records the
serial number of a marketing campaign that generated the sale. The serial
numbers are 8 digits long and located in the second workbook which is a
marketing campaign register. So I need the name of all current marketing
campaigns in the marketing register to be displayed in the dropdown list but
the serial number of the selected campaign to be inserted into the cell in
the sales register.

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