In Excel 2003 help, after entering "specifications" you get...

"Excel specifications and limits"
Cell styles in a workbook 4,000
Custom number formats Limited by available memory

A few years back, in a test, I could get almost 300 custom number formats into Excel.
Also see my free "Formats & Styles" Excel add-in at... http://excelusergroup.org/media/
It can list or remove unused custom number formats and styles.

FWIW, Excel 2007 has a tendency to self create thousands of unwanted and unused styles.
--
Jim Cone
Portland, Oregon USA



"Tonso"
wrote in message ...
Is there a limit to the number of custom formats you can create in a
workbook? I have an application that might required sveral hundred,
and I dont want to get started, then run out.

Thanks,

Tonso