Try this. Make a blank label in the editor with widget "A" with the size and color you want then.....

Place this script in the page.

var info = GUI.widget( "A" ) ;
info.visible = true ;           // this line makes the panel visible
var b = GUI.widget( "eg_1" ) ; // should be caps


Place this script in the button.

b.onPress = function (x,y) {
          info.visible = true;      // makes panel visible
          info.label = "A" ;       // place whatever text between the quotes
          executeActions ( ) ;   // executes before you release the button
} ;

b.onRelease = function ( ) {
          info.visible = false;   // makes panel not visible
          info.label = "" ;      // when you let go it returns to a blankspace
};

// end of script

You can also use the onHold function. Check that out in the P.S. Developers guide .
The onPress function only works with the latest firmware and prontoedit .