Building a calculator with value look up

Hey guys,
I’m pretty new to this all, so if this seems too complicated for a newbie to accomplish that is also good feedback. not sure if this would be the right place to ask something like this but here is goes.

So I am trying to add some functionality to my site. Where the user can type a list of items (text) and a value (a number to 2 decimal places). Then from this, a function that would look up the text value in a database or google sheet document. Then return the corresponding value. (like a Vlookup function in Excel) then the user input value is multiplied by the look up value and the product is returned.

Hopefully to be able to do this with up to 20 items.
Then the sum of these 20 products is also returned.
Finally none of this data is saved. so if the page is reloaded the form is blank.

Thanks hopefully this is possible.