You are light on details. But basically, you would need to check after or
as part of a change, that the new value is not a duplicate. Chip Pearson's
provides several generic techniques which might offer some ideas you can
use:
http://www.cpearson.com/excel/duplicat.htm

another page of interest might be on utilizing events
http://www.cpearson.com/excel/events.htm

--
Regards,
Tom Ogilvy



"Ed" wrote in message
...
I've got almost 30 ranges in my worksheet. No value should be duplicated
in
any of these ranges. Is there a convenient way, either with a worksheet
function or a VBA method, to monitor this for each range? Or do I need to
loop through each cell of each range on a regular basis to see if I've
got
duplicates?

Ed