Assumes column A has the product # & col B has the Quantity

Also assumes the product # IS a number

=IF(ISNUMBER(A2),C2/SUMIF(A2:A50,A2,C2:C50),"")

"Arun" wrote:

My table didn't format well after posting. I reformatted it below.

Product # Salesperson Quanity Percentage
1 Amy 10 **
1 Ron 20 **
1 Jim 10 **
Product # 1 Total 55
2 Amy 15 **
2 Ron 15 **
2 Jim 35 **
2 Bill 20 **
Product # 2 Total 85
3 Jim 35 **
3 Bill 20 **
Product # 3 Total 55