Comparing excel cell pairs in a column for matches or differences in another column

My data consists of two columns of interest, A & B.

Each unique cell should have the same corresponding serial number i.e. each entry for KR0146U09A3 should have the same serial number which it does B150501388, I am happy to drop the A08 and A09 part of the string. Similarly KR0146U21A1 entries both have 0000a000K2008438a as it's serial number.

I am comfortable constructing if statements in excel for string matching but I can't understand how to construct the for loop to loop down through the list for each cell pair.

I guess the pseudocode for the task is: for each unique cell in column A check if the corresponding cells in B are the same.

Can someone provide me with a start as to how I could write a function to do this in excel?

Below is an example of my data:

Cell        Serial Number
KR0146U09A3 B150501388-A08
KR0146U09A3 B150501388-A09
KR0146U09A3 B150501388-A08
KR0146U09A3 B150501388-A09
KR0146U09B3 B150501395-A08
KR0146U09B3 B150501395-A08
KR0146U09B3 B150501395-A09
KR0146U09B3 B150501395-A09
KR0146U09C3 B150501391-A08
KR0146U09C3 B150501391-A08
KR0146U09C3 B150501391-A09
KR0146U09C3 B150501391-A09
KR0146U21A1 0000a000K2008438a
KR0146U21A1 0000a000K2008438a
KR0146U21A2 0000a000K2008438a
KR0146U21A2 0000a000K2008438a
KR0146U21A3 0000a000K2008438a
KR0146U21A3 0000a000K2008438a
KR0146U21B1 0000a000K2008447a
KR0146U21B1 0000a000K2008447a
KR0146U21B2 0000a000K2008447a
KR0146U21B2 0000a000K2008447a
KR0146U21B3 0000a000K2008447a
KR0146U21B3 0000a000K2008447a
KR0146U21C1 0000a000K2008404a
KR0146U21C1 0000a000K2008404a
KR0146U21C2 0000a000K2008404a
KR0146U21C2 0000a000K2008404a
KR0146U21C3 0000a000K2008404a
KR0146U21C3 0000a000K2008404a