Need to be able to query a feild in frontpage, is it possible

For a web based reseller interface for my internet service we have a simple page made in frontpage.

Basically what I want is a text box that can only accept the numbers 1,2,3,4,5,6,12 these numbers would be the amount of months the customer would want to pay for. Deppending on what number has been typed, there needs to be another text box that will display a price. Say the number 1 is typed the price box would display $16.95. But if 6 months would be typed it would display $95.70 (15.95x6). 12 Months would be $179.40(14.95x12). If someone were to type a 7,8,9,10,11 it would either say thats not a correct amount or it would delete the contents of the text box.

I don't know how to do this, or if I can. If there is another code that will allow me to do this please help me or let me know.

php will be able to do this, java-script.. maybe (dunno)

but im pretty sure html wont be able to

www.yourhtmlsource.com i read some html tutorials there a while ago~~ you can check yourself if they got what you are looking for