My VBA creates an error in a formula

Hi,

I've got an Excel workbook, with a built in macro that runs when you choose an entry in the two combo boxes.

IF you then try to change the value in B9:B15 or B22:B25 then an error message pops up and says that the sheet contains a formula with an error.

If you do not change both the combo boxes, then no such error shows up.

I've looked through formulas etc, but I can't seem to find the error. I hope that some of you might be able to give a guiding hand.

See attached file