Insert Message template to an Add form

Hi,
I am using ver 9.8.
I need to insert a list of message templates to an Add form.
Details:

1. 2 Tables: Message_Template and Message_Send
   
2. Message_Template keeps a list of frequently used text.
   
3. Message_Send - a table to store the message sent to users.
   
4. When i create a message using the phpr form generated from Message_Send table,
   Beside entering the message into its text field of the Add form manually, i would like to have a button or link beside the text field,
   to click and open a popup of the message_templates, and i can choose the frequently used text from the Message_Template.
   
5. Upon selecting, it will copy to the message text field automatically.
   I have read the help and forums on popup window, and button events
   
   but i am not sure how to put them together after 2 days of trying, especially how do i
   
   obtian the value from the select of the message template popup.
   Any ideas and advices will be greatly apprecaited.
   ACP