Need help with rsgp site? (Not for rsgp)

hey all. So I am in a corner with my new website. I need some help it really just an answer to a quick question.

So I'm looking for either a plugin, or some form of code that would allow my site to function like this:

-user inputs ammount of gold they want to buy in "box A" (already themed with css)
-the USD ammount of their order is displayed in "Box B" (also already implemented on my site with css)
-users then press the "buy" button located under these 2 boxes and it then grabs the information that the user entered and redirects them to a WooCommerce checkout.

That's it. Everything else on my site is done and ready to go, except for the shop itself lol. Can anyone help me by linking some videos, plugins, or explaining how gold sites like Arcus accomplished this?

Thanks

 

Hey, try ezform calculator plugin its exactly what you asked for =)