You need to remove the acn entry from AutoCorrect options in Excel 2007
(Office Button, Excel Options, Proofing, AutoCorrectOptions). In Excel
2003, if you move back over the cell that changed to CAN, you should get an
AutoCorrect smart tag that you can use to revert back to ACN. If not, do
the same as Excel 2007 option. Delete the entry from AutoCorrect (Tools,
AutoCorrect Options).
Stephen @ ZennHAUS
I have the 2000 version & it doesn't support this.