sorry I may have misunderstood.

I have upto 700 rows which i want to compare and use the formula above.
By leaving it as:
IF(A1&C1=3DE1&F1,"A",IF(B1&D1=3DE=AD1&F1,"B","C"))

Wouldn't each formula always check row 1? So I want to put this
formula in each row at column G but if I put the above in row 35 would
it check row 1 and give me that result?

So rather than manually change this upto 700 times to reflect the row
it's in - can this be done some other way?