A macro to find which accounting entry hasn't pass in another system

Hi, first of all sorry for my english it is not my first language so if it is not clear don't hesitate to ask for more information.

I work in accounting and I am trying to find a way to search for transactions that hasn't pass in an other system. In order to simplify my question I will use only 2 columns in my example. So I have Column A and B as shown in my link:

imgur.com/JUUqHi8

Is it possible for a macro to descend the column A and find the first identical value in column B and then go to the next value in the column A and do the same? This way I would not have the "unique" 75 identified in my image as a duplicate when in reality the 75 didn't pass in the other system or column B.

Thank you for your help, I have been trying to find a solution to this since it would save me a lot of thing considering that I compare systems with more than 5000 accounting entries and the column A sometimes have a lot of the same amount even though it is not the same transaction.

As far as I understand there are two possibles results. If there is a duplicate value in A

aa_checker.jpg

or if there are no matching value in the B column

aa_checker2.jpg

where the value 18 is only found in the A column is that correct?

Alf