Hi,
all you need is two small scripts in the printed fields prePrint and postPrint events:
prePrint event
if (!this.isNull) {
var cStr = this.rawValue,
cMaskString, cKeepStr, cAsterisk,
iLength = cStr.length;
// Save rawValue as a global variable (don't use var!)
cGlobalStringVar = cStr;
// Replace except the last for characters with asterisk.
this.rawValue = Array(iLength-3).join("*").concat(cStr.slice(iLength-4, iLength));
}
postPrint event
// Restore to original raw value from global variable
this.rawValue = cGlobalStringVar;
Hope this helps.