* Open the desired request template and Navigate to Field and form rules.
* Click "on field change" and create new rule.
* Set rule execution as "On Create / Edit"
* Set "Execute script" as action.
* Add the below script
var x=$CS.getValue("WorkOrder_Fields_UDF_CHAR1");
var y=$CS.getValue("SUBJECT");
$CS.setValue("SUBJECT",(y)+" -"+(x));
* Click Save script.