Need Help: Forumula Sum Weight

Need Help: Forumula Sum Weight

How would I go about making a field or series of fields to calculate weight...

Example application:

Application for Campers to determine their packload based on the contents they add to their pack.

Add Item Form:
-Item Name Field
-Weight Field
-Included/Excluded radio button

If I have an item that weights 3lbs 4oz how would I add this without having to calculate the item in a calculator converting to a dec place? I would then like to sum that value at the end in my view to determine what the weight of the Items I "include" in my pack weigh.

I would like to be able to have this value change depending on whether or not the item is "included"

e.g.

3 Items[/b]

ItemA (included)
3lbs 1oz

ItemB (Included)
1lb 12oz


ItemC (included)
2lbs 3oz

Total Sum = 7lbs (itemA+ItemB+ItemC)

IF WE EXCLUDE ItemA

Total Sum = 3lbs 15oz (itemA+ItemB+ItemC)