If the sheet is protected, you can't change the cell's Data Validation.
So, if you typed the list in the Data Validation dialog box, you won't
be able to modify the list.
Instead, you could use a dynamic list on an unprotected sheet, and add
entries to that list. There are instructions here for a dynamic range:

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

And for using a name in data validation:

http://www.contextures.com/xlDataVal01.html

Kane wrote:
I have a unlocked cell, with Data Validation, List. With sheet protection
activated I cannot "add" to the cell contents supplied from the List
function. If sheet protection is off, this is possable. Is there a way to
have this feature with sheet protection turned on (activated)?


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