Adding PopUp Message depending on $Total$

We would like to have a message pop up when the subtotal on the order is less than $200.

I've already tried Form Personalization ...

Seq:   10       Description: Subtotal Under $200      Level: Form     Enabled

CONDITION:       Trigger Event:  WHEN-NEW-FORM-INSTANCE

                         Trigger Object: ORDER

                         Condition:   :ORDER.SUBTOTAL < 200

ACTION:         Seq 10

                       Type: Message

                       Message Type: Show

                       Message Text:  Order Subtotal is under $200, consider adding $10 handling charge.

Any ideas??