I am trying to compare a later version of a list with another. There may be multiple occuancies of values in each, or the later list may have additional unique values. e.g.
A A
A A
B A
B B
C B
D C
D
E

I've been trying to 'mark' where the lists start to match and then count how many new values I have. I started with a simple IF(A1=B1,"",1) and then wanted to simply insert a cell above the change value in the first row expecting the formula to increment both sides of the test. Unfortunately it only increments the side where the insert has been done so every cell below is still out of line. I've tried IF(CONCATENATE("A",ROW())=CONCATENATE("B",ROW() etc but this just results in a text comparison rather than a cell reference so fails every row! Is there any way I can accomplish this?
p.s. I'm using an work computer and can't install any add-ins.

Thanks in advance.