Sorry I want to clarify.... My first post confused what I really want to do.
Use this as an example. A customer purchases one package of bags they get charged $4.00 for shipping anywhere in the USA. If they purchase a second its an additional $1.30... and for the third its an additional $1.30 etc. (Each product would have a different amount for the shipping)
Otherwise I think I need 2 more fields in the database and just use those correct? Has anybody else done shipping like this? Both of the shipping providers that I can buy do not work this way.