function encryptcardno() {

var strString;
var strChar; 
var strXXX; 
var strNew;
var i;
var strEncrypt = "XACFRTKQLP";  // corresponds to 1234567890

strString = document.forms[0].cardno.value ;
strNew = "";

for (i = 0; i < strString.length; i++) 
	{ 
	strChar = strString.charAt(i); 
	strXXX = strEncrypt.charAt(strChar); 
	strNew = strNew + strXXX;
	} 
document.forms[0].cardno.value = strNew;
}