how can i find the cells that add up to a specific value

I have a list of values that ought to match an external list. There is a discrepancy that does not match any single cell so it must be the sum of two or more cells, so I need to find them but the list is way too long to do by hand. Thank you in advance

I would be inclined to use Vlookup to compare the values and then filter by N/A to find the discrepancies.

Difficult to suggest any search strategy when we don’t know the nature of your lists, nor of the matching between them.

Detail please.