I just checked and for some strange reason when using the MAD function the data can’t be in Currency or Accounting format. It can be formatted as General, Number, Percentage, Fraction or Scientific. The software that calculates MAD uses Excel’s MEDIAN function. In Excel MEDIAN works fine with currency data, but produces an error inside the software program (VBA).
I have not checked all the various functions to see whether this problem appears for other functions, but it does not for the few that I have checked.
Thanks for identifying this problem. For now it is best not to use MAD with currency formatted data.