Okay, top of my head stuff now, as it's getting late:

You could have a MAX function in column D to find the highest value of
the three, and a MIN function in column E to find the lowest. Then in
column F a CHOOSE function to get the third value. The third value
obviously sits in between the other two, so in two more columns you
could measure the difference between this and the highest and lowest
values - maybe this is the starting point to determine if one of the
numbers (it can only be either the max or the min vlaue) needs to be
adjusted.

Too late for me to elaborate ... just some thoughts ...

Hope this helps.

Pete