Im using this script to copy from one to another textbox. I dont know how to make when i write in box A that what will be copied in box B to be changed. exp. Letter A ti be 001, letter E to be 002, letter V to be 008. I dont care if its in php or JavaScript.

Thanks for your time and help

Code:
<html>
<head>
<script type="text/javascript">
    function copy_data(val){
     var a = document.getElementById(val.id).value
     document.getElementById("copy_to").value=a
    }

    </script>
</head>
<body>
From:<input type="text" name ="a" id="copy_from" onkeyup="copy_data(this)"/><br>
To:<input type="text" name ="b" id="copy_to"/><br>
</body>
</html>