Drop down lists: including formulas

Hello,
I am wondering if anyone can help adding a formula to a text cell of a drop
down list. I understand how to generate a drop down list, however I am stuck on the formula.
This is the best way i can explain it:

The text in the drop down list might be:
- a pinch
- a hand full
- a shovel full
- a wheel barrow full

Each text cell has a formula with a number (e.g. =24) that would
auto sum in a total column. I hope I explained i properly. Any help would be
greatly appreciated.

PS I know I can do it by adding another row but I would like it included in
the down list to keep it simple and clean. Thanks.

Tom

I hope this helps explain what I am looking for. This is a sample I sent to a friend, but he couldn't help me.
Basically I would like to have the data that is in column K in column J in each cell they are beside. The long and short is I would like the numerical data to auto sum in the total column and the text to stay (show) in the cell that is chosen from the drop down list.

Thank you for your help, however I don't understand your suggestion. I am not sure where I should enter you formula? I tried it in the TOTAL column and it came up FALSE. Any further information would be great.