I'm not sure what you are missing... Let's take the cart out of it for now.
You want to populate a list in dreamweaver with the results from a table (options) then you want to submit that form and filter a recordset to return the result they chose (filtered by the list selection) so that you can get the weight and price.
With or without eCart that process is the same... and if you are able to get that data you can then bind it to the shopping cart.
Sounds like you can do everything from the Recordset simple view since you are filtering with just one value.
Let me walk you through it with numbered steps so you can tell me where you are getting stuck. I'll ignore whether you have a shopping cart or not because it is irrelevant.
1) Create a recordset that contains all of the available options
2) Add a list to the page to display those options as part of a form
3) Create another recordset (I often use the same one with complex SQL but it is more simple to just do another) that is filtered by the selection in the option list and returns the associated price and weight
Are you able to accomplish those steps? As you can see they use only existing DW functionality and require no hand coding... probably not even the advanced view of the recordset just the simple one.
Once those steps are accomplished... update you add to cart and bind the price and weight fields to the recodset you created in step 3 above.
