Compare data pairs

I do not know if it can be done using excell formuals, but i have a task:
i have a table of 3 columns and about 15000 rows of data. I'd like to find a formula or a set of formulas that should compare the pair formed by "A" and "B" columns and if it finds a match with a deviation of 3% to display the values of the "C" column. So basically, if , let's say it finds the pair 'A52 and B52' that is not bigger or lower then 3% of another pair , let's say 'A3000 and B3000', to display the two values, 'C52', respectively C3000. Since the values in those 15000 rows are with a lot of digits i am forced to use those (+/-)3%. i hope someone can give me an idea where to start.