Formula for excel (return largest number for subtraction of different cells and which cells were used for answer)

I'm trying to retu the largest number for the difference of different cells - ie, retu largest number after computing a1-b1, a1-c1, b1-c1. Assuming a1=3 b1=2 c1=1 then number retued is 2 (as a1=3 minus c1=1 gives 2.). I also want to be able to tell that the answer came specifically from a1-c1, or whatever the case may have been. Actual amount of cells is far higher than the three given, so doing each equation in a separate cell is not feasible. Thanks for any help!