grid = new Grid(twoColum, SWT.BORDER | SWT.V_SCROLL | SWT.H_SCROLL);
viewer = new GridTableViewer(grid);

grid.setData(RWT.MARKUP_ENABLED, Boolean.TRUE);
grid.setItemHeight(ROW_HEIGHT);

Template template = new Template();
[ template stuff ]
grid.setData(RWT.ROW_TEMPLATE, template);

grid.addListener(SWT.Selection, new Listener()
        {
            @Override
            public void handleEvent(final Event event)
            {
                JavaScriptExecutor executor = RWT.getClient().getService(JavaScriptExecutor.class);
                executor.execute("console.log(\"test2\");");
            }
        });

grid.addListener(SWT.Selection,
                new ClientListener("function handleEvent(event){console.log(\"test\"); };"));