[ic] Update price to reflect options on flypage

[james]

Dear list,

I have had a good look around the mailing list archives and have been 
unable to find a solution to this problem, so was hoping someone on 
here may be able to offer some help.

I have an item which has a material option that adds on an extra cost, 
e.g.

Silver - £100 (base price)
8crt Gold (add £50)
18crt Gold (add £250)

We would like it so that on the product display page selecting one of 
the more expensive items would automatically update the displayed price 
(where we currently use the [item-price] tag) for the item.

I'm thinking this would probably require the <select> to post the form 
to the same page and then a perl method that manually calculated the 
new price before display. However, I am stuck as where I can obtain the 
added cost value that the user has selected.

Ideally once selecting an option the dropdown would reflect the choice 
so the options from above would then look like...

Silver (deduct £50)
8crt Gold
18crt Gold (add £200)

Saving the user from doing any mental maths.

TIA for any pointers.

James Turnbull.