data validation - cell lock
 

Hi

A little while ago I posted a question on how to get a multiple option
dropdown using the
data validation option (unfortunately I can't seem to find the thread).

The solution suggested worked great. The user select an option in the
dropdown at the
top of the spreadsheet which then altered the options available in the rest of
spreadsheet.

Example
Select Option A at the top and only 1,2 and 3 are available in the dropdown.
Select Option B and only 4,5 and 6 are available.

It used the following code in the data validation:
=OFFSET(ActivityStart,MATCH($B$3,ActivityColumn,0)-1,1,COUNTIF(ActivityColumn,$B$3),1)

However it has one problem, unlike a normal data validation the user can
type over
the options provided with their own selection. I want to lock it down with
just my
choices.

Is this possible? Any suggestions greatly appreciated

Rexmann (using excel 2007)