Hi.
Excel normally does sort on the formula result, but what may happen is that the act of sorting may change the results for some or all of the formulas.
Try turning calculation to manual to see if this is your problem.
Set calculation to manual, do the sort, look at the results (which should be based on formula result), then calculate (either using f9, or by setting calculation back to automatic) and if the results then change, then that's your problem.