Manila Messaging - Alternate Messenger HELP!!!

[menace2society]

When I receive a message, I go to the appropriate tab, then read my message that shows on the screen using Manila2D. When I click the middle button on my Titan 6800, the conversation shows (tmail)
Is there a way to have another messaging program to show when you click on the message. I want to use SMS-Chat and still be able to read my messages on the home screen. It's just that when I want to reply, all I have to do is click on the middle button or the icon in the upper right hand of the screen and the conversation of that specific person shows up, except i want SMSChat to come on instead of the standard threaded text messaging app. Thanks