Excel Conditional Formatting if one column is equal to another

This should be the simplest example of conditional formatting but I can't figure it out.

I have two columns seperated by several dozen other columns (C-original data, BO- calculated value) and I need to highlight the calculated value if it is not equal to the original value.

I can do this on a cell by cell basis but can't see how to apply it to a whole column without adding a rule for every row (there are many 1000s of rows).

What am I missing?

Solution 1:

I tend to use an IF() rule for this sort of thing. The trick is then to get the '$' signs right. If column C is the original data and BO is the calculated value, then select the BO column and add a conditional formatting formula rule of:

=IF($C2=$BO2,1,0)

Note there is no $ sign beside the row number, which causes it to apply to each row in turn.

Solution 2:

Select column BO and use the following:

=$C2<>$BO2