i was wondering if there any way to reset the value back to Zero if certian value found for example

i have got an formula on excel whereby it calculate and add all the "

**S**" from a range "B11:AF33" however is there anyway also back to

**0**value if "

**ar**" found within the same range "B11:AF33"

below it is the formula that counts all the "S" and add the result in to cell number "B6"

**=SUMPRODUCT(LEN(B11:AF33)-LEN(SUBSTITUTE(B11:AF33,"s","")))**