Richard,

Running any sort of macro that changes anything in the Excel on a worksheet
will clear the Undo buffer and disable the Undo/Redo buttons.


--
Cordially,
Chip Pearson
Microsoft MVP - Excel
www.cpearson.com


"Richard" wrote in message
...
What would cause the Undo, Redo buttons on the toolbar to
stop working. Is there a way to reactivate them.