Excel 2002, Windows 2000 SP4

I have a simple formula that takes a number in column A divided by a
constant cell in Column B to return a number in Column C and round to one
decimal point (ROUND(A3/$B$2,1)).

Then, I sum the results (Column 3) to come up with a number (=SUM(C3:C6)).
So far so good.

Problem: I need the Sum of Column 3 to ALWAYS equal 40. This may entail
changing one or more entries in Column C (or maybe an interim column if
necessary) by a tenth-place decimal +/- to come up with 40.

Any suggestions for how to do this? I'd prefer a formula, but will do VBA
if necessary. Thank you for your help.