How to mass highlight data

Hello! I have basic ability when it comes to Excel. I need to examine data that was transferred to a Pivot Table. In one column, there are many different categories under four character codes. In another column are basically 11 sub-categories. I need to find a way to easily highlight the data that does not belong together. As an example, in the first column, there could be items like 03AB, 7715, 5616, 18AE. In the second column, some examples would be Missing Activity, Login Issues, Tech Support. Some of the items in the second column should ONLY be matched to certain items in the first column, and I need to point out the errors. It is too much data and too tedious to go through it line by line as I did last month (took over 14 hours....) Any help would be greatly appreciated! Thanks!