calculate difference of columns with different amount

Hello,

I would like to calculate the difference of columns and percent deviation to the first column. for example column A has 6 rows is basis column B has the same size. column C and so on. The size of columns should be variable. Should I do it with a loop and a table to variable (column B, C etc.) so I choose the header used for the calculation. column B - column A, next loopstep column C - column A …

Thanks in advance!

Oliver