GroovyFX - Custom UI widget/component

[Tx. T]

all,
I am trying to build a somewhat application specific (custom) widget (or 
control) that includes for example, 3 pushbuttons.
class ThreeButtons extends BorderPanel { ... }
&& use this in my application:
start { stage { scene { threeButtons (label1: 'one', label2: 'two', label3: 
'three') } } } 
Would someone please point me to where can I find such example?
Or do I need to write the ThreeButtons in JavaFX and register in Groovy to use 
it?  Thanks!
---Tim