How to compare two strings and find the difference

Hi all, In the middle of a search, I have two string fields, one is called A and the other B (both have the ";" as delimiter but the number of values inside is variable): **A=test;sample;example B=test;sample;example;check** I would like to compare the two string and have the difference as result in a new field called C (so suppose C=check). Is there any way to achieve that (like doing an Excel VLOOKUP without performing a sub-search that can affect the search performance)? Thanks a lot, Edoardo