((DiagramEditor)getDiagramEditor()).getEditDomain().getPaletteViewer().addPaletteListener(new PaletteListener() {
			
			@Override
			public void activeToolChanged(PaletteViewer palette, ToolEntry tool) {
				System.out.println("Tool Changed");
                               //You can put here the code to analyse if the tool clicked is the one you want
                               //and call whatever you want
				
			}
		});