Question [Q] App question- not sure where else to post this

I use a cell phone (samsung illusion) hooked up to a PC that is used for sending out a large number of text messages to our mailing list. However, sometimes people want to unsubscribe from the mailing list. Is there an app, or some adb trickery I could use to make it so that I could have it automatically block outbound texts to a number when someone texts back STOP? Right now I am manually removing people's number from the mailing list.