What is the Microsoft Excel FORMULA that I need to use to calculate percentage of sales?

This is what my Excel WS looks like. I need to figure out the percentage of sales formula to put in. Please help!!

Quantity       Wholesale Cost        Subtotal         Percentage of Sales

5                          $24.99               $124.95

10                        $14.99               $149.90

8                          $19.99               $159.92

2                          $239.00             $478.00

4                          $49.00               $196.00

2                          $249.00             $498.00

10                        $9.99                 $99.90

8                          $29.00               $232.00

                                         Total  $1,938.67

This is what the percentages should end up being in the chart

10% 

20%

16%

4%

8%

4%

20%

16%

How do I get these percentages? Whats the formula?