That means formulas in cells in the same region of the sheet are different.
It's just Excel trying to be helpful. For example:
A1 formula: =SUM(B1:J1)
A2 formula: =SQRT(Y100)
You can probably ignore that message. To turn off those messages goto the
menu Tools>Options>Error Checking tab>Rules. Uncheck the items you don't
want to see messages for. I have all of the error checking rule settings
turned off.
