Using Tasker, you can choose an action; in this case, the one you want is listed under Phone (left). Tasker lets you enter a variable so that the number you send will be whoever just sent you a text (right).
For the Message field, type whatever you want your text to say, such as I'm in a meeting now and will get back to you when I can. When you're finished entering your message, tap twice where it says Action Edit Send SMS at the left of the top nav bar — first to save your task and go to this task's main screen, and second to go back to the Tasker home screen.
Note: If you want to also silence your phone, you'll need to create two separate, additional tasks. Once again, click on the Tasks tab on the top nav bar and then the + icon in the middle of the bottom nav bar to create a new task. As before, name it whatever you like. I called the first one "Meeting START Silence" so I'd remember what it does. Again, click the + icon to add an action, and use the Audio option to set the ringer volume, media volume, notification volume and system volume all to 0. For example: Go to Audio / Ringer Volume and move the Level slider to 0.
(Tasker also has a Silent Mode action, which would be easier, since it's one single action to mute the phone — but unfortunately not all Android devices support it. Feel free to try it and see if yours does. )
Add a second task to unmute the phone (I named this one "Meeting END Silence"). Do this by returning to each of the phone audio settings you muted in the prior task and putting the volume levels back to where you want them. (If Silent Mode in Tasker worked for you in the previous step, simply turn it off with this task.)
3) Next up is creating a new Tasker profile to tell your phone what should kick off your Meeting Autorespond Msg action.
While you actually want the trigger to be "Whenever I get a text message during a meeting," your initial triggering context in Tasker is simply going to be "My phone has received an SMS message" — even though you don't want an automated response sent every time you get a text message. Don't worry — we'll refine this soon using the Trigger app, which will read your calendar events and turn your autorespond on and off accordingly.
First thing you have to do is set up your profile.
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