Need help to make Return Reason field as mandatory field through OM extension

Need help to make Return Reason field as mandatory field through OM extension

have used the below code, but it did not work

import oracle.apps.scm.doo.common.extensions.Message;

import oracle.apps.scm.doo.common.extensions.ValidationException;

   def lines = header.getAttribute("Lines")

  

    while(lines.hasNext() ) 

    {

    def line = lines.next()

    

  

    if (line.getAttribute("ReturnReasonCode") == null &&

      (LineCategory == "RETURN")

  )

     

 {

  

  def token = [LINE_NUM: line.getAttribute("DisplayLineNumber")];

String msgtext = ("Return Reason is Mandatory")

Message msg = new Message(Message.MessageType.ERROR, msgtext);

throw new ValidationException(msg);

 }

    }

Regards