Try using an onChange event on the dropdown to call a function that does 
the calculation for you.

At 12:55 04/10/01 +0000, you wrote:
>I have a form which asks a user how many to enter a number of subscribers
>and i want to display a cost dependant on what number they enter, i would
>like the cost to appear within in a form field or just as text beside the
>field where they have entered the number of subscribers, how do i do this?
>
>to illustrate what i want to happen:
>
>how many subscribers do you want: (user entry form field - blank) cost:
>
>user enters or selects form dop down
>
>how many subscribers do you want: (user entry form field - with user
>entered value) cost: (automatic cost appears)
>
>What is the cleanest way to do this bearing in mind there are more details
>belwo this form to be filled in before it is submitted, i just want the
>user to see the cost before they submit the form.
>
>cheers
>Duncan