Write A+B=B+A with Excel Function

Hi all,

I'm trying to build this model A+B = B+A with Excel function (pls let me know if this can only be done with VBA, i'm not too sure)

Criteria:
* A+B = B+A at all times
* Require to check if this A+B = B+A is true
* If not true, show the difference
* A+B = some value
* B+A = some value
* It's possible that the value of A+B does not equal to the value of B+A
* Be prepared for the subset content of A and B to expand...I've thought of listing out all possibilities and checking with vlookup but it would be too much to maintain when this grows to millions of pairs.

Thanks,
Yami