Welcome to the board.
The arguments for the function are ( array, percent), so you don't have a lot of leeway built into the function to adjust that array. If you can figure a way to make a single argument for "array" that already discounts the two values you don't want, then that would do the trick, but that's going to be messy and likely hard to explain (or recall later) when you try to audit or duplicate the process. So my suggestion is to arrange a 'helper' array of values (because you'll still want to have an array consisting of four values), that has already removed the two cells you want to ignore, and operate on that array. Having that 'helper' array constructed on the worksheet somewhere, even if it's later hidden for cosmetic reasons, will make the thing easier to explain or do again in the future sometime.