How do I set a GUI button's text using a string from another script?

I want to define the text if a GUI.Button using a string array, but my string is defined in a different script.

For example:

 var tacticalvariable : tacticalvariables;
 tacticalvariable = gameObject.GetComponent(tacticalvariables);

 
   OnGUI () {
     for (var i:int = 0; i<=5; i++) {
        GUI.Button (Rect (270, 10 + (60 * i), 120, 40), tacticalvariable.phaser.FireMode[i]);
        }
     }
 

where tacticalvariable.phaser.FireMode[i] is a String array that is defined in tacticalvariables.js

I can't get anything to show on the button though - why not?