Hi Tammy,
Say your data is in columns A and E,
Input a helper column F
In F1 put =IF(A1=E1,"","Error")
Click on the fill handle and drag down as far as is needed.
It will return an Error when they aren't equal otherwise a blank.
You could also do it with conditional formatting.
Select all of your data in column E making sure E1 is the active cell
Go to Data>Conditional Formatting
And set Formula is =A1<>E1
Click on format button and set a color for the cell
from the patterns tab and OK out.
HTH
Martin