Hey Wolf,
I think I know what you mean.
Just set the trigger up as normal. If you enter any text in the text field this will be displayed instead of Alpha etc.
To hide them and make them unsuable, the text needs to be "NULL".
So you can hidereveal it whenever you want by putting in another trigger
0 setradiomsg "text"
If "text" is "null" this will hide it, otherwise it will be revealed.
0, 1, 2, etc. refer to the radio callsigns e.g 0 is alpha, 1 is bravo etc (actually it may start on 1 - not sure)