1. Under Admin >> Incident Template >> Edit the template in question
2. Choose field and form rules and apply the below script On Form Submit
var duebyDate = $CS.getValue("DUEBYDATE");
var currentDate = new Date();
if(currentDate>duebyDate)
{
$CS.mandateField(["WorkOrder_Fields_UDF_CHAR1"]);
}
You can choose the relevant field name as highlighted below