prevention of use for [return] and [backspace]

We are using a simple selfmade cgi-script for our ordering system. Now we are looking for a small piece of script wich prevent that a user can use the [return] and/or [backspace] in the ordering-system. It is a simple script wich you can use on your own server to try. We only need a prevention for the use of [return] and/or [backspace].