Working with Forms and interdependent fields (1 Viewer)

Hi There,

New to the forums here but, I have an educational problem I need to solve I am most of the way there but have run into the realms of beyond my experience.
I need to create a precious metals to currency converter that displays USD, GBP and Euro prices. The conversion bit is fairly straightforward but I need to place all this in an interactive form that appears on a html page.
I am trying to create a rule that if a client chooses a particular metal that the rate will automatically publish in another field.

So for example Field Metal has a list limited to 9 carat, 18 carat, Platinum and Silver. I am trying to get the Rate field to automatically populate by reading from a csv file or it's own lookup with the relevant rate so sort of

if [Metal] = "9 carat" [Rate] = 11.87
Fairly new to programming so bear with me if I am not being clear.

Thanks in advance

Cxtroen

One way would be to have a combo box that uses a table with the various values, and this to populate the rate:

http://www.baldyweb.com/Autofill.htm