Excel Conditional Formatting if one column is equal to another

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.

Select column BO and use the following:

=$C2<>$BO2