Ok, let's assume the source range for the combo box is I1:I10.
The linked cell is A1.
Use this formula to get the actual selection:
=IF(A1="","",INDEX(I1:I10,A1))
This is one of the drawbacks of using a combo box. You have to use an extra
step to be able to actually use the selection. But.....if you want the drop
arrow always visible this is what you have to do.
A little trick is to put this formula and/or the linked cell in a cell
that's under the combo box. That way it "appears" to work just like a data
validation drop down list. All you'll see is the selection in the combo box.
Here's a screencap to show how this would work:
http://img209.imageshack.us/img209/9852/comboboxjw9.jpg
In the screencap I use B3 for the linked cell and C3 contains this formula:
=IF(B3="","",INDEX(I1:I10,B3))
As you can see the entries in both of those cells, B3:C3, are hidden because
the combo box "sits" on top of them. Then, if you want to use the selection
from the combo box in a formula you just need to refer to cell C3.