Best way to get a specific cell value from grid

<?init class="org.zkoss.zkplus.databind.AnnotateDataBinderInit" ?>
<zk>
	<zscript>
		import org.zkoss.zk.ui.util.GenericForwardComposer;
		
		public class Car {
			private String makeModel;

			public Car(String m) {
				setMakeModel(m);
			}

			public String getMakeModel() {
				return makeModel;
			}
			public void setMakeModel(String m) {
				makeModel = m;
			}
		}
			
		List Cars = new ArrayList();
		Cars.add(new Car("Bugatti Veyron"));
		Cars.add(new Car("SSC Ultimate Aero"));
		Cars.add(new Car("Saleen S7 Twin-Turbo"));
		Cars.add(new Car("Koenigsegg CCX"));
		Cars.add(new Car("McLaren F1"));
			
		public class myController extends GenericForwardComposer {
			public Grid myGrid;
			
			public void onClickButton(Event event) {
				Object clickedCar = event.getOrigin().getTarget().getAttribute("theMakeModel");
				alert("You clicked on the " + clickedCar);
			}
	
		}	
	</zscript>

	<window id="main" apply="myController" style="padding: 25px;">
		<grid id="myGrid" fixedLayout="true" model="@{Cars}" hflex="min">
			<columns>
				<column label="Make & Model" width="150px" style="font-weight: bold;"/>
				<column width="100px" align="center"/>
			</columns>
			<rows>
				<row self="@{each=Car}">
					<cell><label value="@{Car.makeModel}" /></cell>
					<cell>
						<button label="Tell Me" forward="onClick=onClickButton()">
							<custom-attributes theMakeModel="@{Car.makeModel}"/>
						</button>
					</cell>
				</row>
			</rows>
		</grid>
	</window>
</zk>