Insert a drop down list?

Hi Guys and Gals,

I'm currently running a spreadsheet (very early days) where the operator inputs a device type and thickness in cells Ex and Gx respectively.

Using a lookup function and some nested calculations, cell Hx is then populated using data in another workbook.

However, the entry of the device type in cell E is causing problems, as the lookup function does not accept some of the operators shorthand versions.

To avoid this problem, I'd like to insert a drop down list that the operator can select from. This drop down list needs to be available on every line in column E.

I would ideally like the list populated from my other workbook, so that can be kept seperate, and the list updated automaticvally from the other workbook. Is this possible?

Thanks for any help,
Gavin.