- Select your range. Let's assume that your range is A3:E10.
2. Home tab > Conditional Formatting > New Rule > Use a formula to determine which cells to format and put following formula and choose appropriate Fill Colour
=COUNTIF($A3:$E3,A3)>1
(Note the formula is dependent upon the your starting cell in the range. If A3 is not the starting cell, then you will need to replace $A3 and A3 appropriately)