Start with the "three-button dialog" available in your palette. Unlike the one and two button variety, it is a plain subVI with diagram.
I has a string indicator and the diagram is visible to the programmer, just double-click it. Inside, look for "Three button dialog CORE.vi", It contains a monstrous 7 stage sequence structure containing all the logic to resize the text indicator, etc. Just gut it out for your purpose and save it under a new name. Good luck!