Are you trying to use these 300K named ranges in Excel formulae or in VBA?
can you give an example of the code/formulae you are using?

regards
Charles
______________________
Decision Models
FastExcel 2.2 Beta now available
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"Charles Williams" wrote in message
...
yes, performance will be very slow. 300,000 named ranges is not a good
idea.
You can probably reduce the number of named ranges by a large factor by
using implicit intersection.

Charles
______________________
Decision Models
FastExcel 2.2 Beta now available
www.DecisionModels.com

wrote in message
oups.com...
I've already posted about a similar issue with creating the named
ranges and have successfully created all 300,000 needed for a
particular project I am working on...however, is having 300,000 named
ranges going to result into performance issues with Excel at some point?