Create a named range with your list of options, e.g. MyList. There are
instructions here:

http://www.contextures.com/xlNames01.html

Choose Insert>Name>Define
Type the name: NoList
In the Refers to box, type:

=OFFSET(Sheet1!$G$1,0,0,0,1)
You can change the Sheet1!$G$1 reference to a sheet and cell
in your workbook

Click OK

Select cells A1:B1
Choose Data>Validation
From the Allow dropdown, select List
In the Source box, type:

=IF(COUNTA($A$1:$B$1)=0,MyList,NoList)

Click OK

Keith wrote:
> Two cells, using data validation | custom... COUNTA($A1:$B1)<2
> This works fine to prevent data in both cells.
> But I also want to use a drop down list for the data selection in A1 and B1,
> How can I do both?
> Thanks,
> Keith
>
>
>


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