RTB Radio message

Need a little help figuring this out - I have a C130 and 135 flying around for refueling. Of course, when they run out of gas, they RTB and head home. More than once they've caught us in the middle of refueling ourselves, always takes us by surprise because of the sudden change in course and dramatic altitude change.

What'd I'd like to do is simply have them yell out "RTB'ing to base" or whatever generic message DCS has built in. I'm not quite sure how to trigger this? I've poked through the ME and see a few things, but don't understand how to trigger it. I also use MOOSE, but seeing as how I'm still brand new to it, not sure how to get messages to trigger using it?

Any input is appreciated!

Here's a quick and dirty script I just made drinking my coffee at work. You will need to load MIST before executing this script.

Mind you, this will not tell you exactly when Texaco will actually RTB but it will warn you that it is low on fuel. Change 0.25 for a lower value if you want.

function callLowFuel()
   remainFuel = Unit.getByName('Texaco'):getFuel()
   if remainFuel < 0.25 then
       trigger.action.outText('Texaco low on fuel', 10, true)
   end
end
do
mist.scheduleFunction(callLowFuel,{},timer.getTime() + 60, 120)
end

You can refine it further by unloading the function from memory if you need that. Remember to change the unit name or the fuel qty as desired. Fuel qty is a number between 0 and 1 unless that particular unit does not carry external fuel tanks in which case the qty is bigger than 1