I have two columns one with heights (i.e. 6'6", 6'7" etc) and one with weights say column I and J. In another cell C2 I would like to be able to enter a height, while still displaying height, yet for a calculation use the corresponding weight.
Vlookup is the answer - providing the list of heights is in ascending order, and has no duplicates - otherwise you will need to use some other unique identifier, or method.
Your calculation will use the height from C2 (if height is used in the calculation) and where in the calculation you would use the weight, there you use Vlookup to scan down Column I until it found an exact match to C2 then grab the value from that row in Column J