The HTML element properties allow you to add IDs, CSS classes, custom attributes and client-side JavaScript event processing to individual controls.
For this example, we'll add an onmouseover event to a button control.
Add a button to your form. Add some text.
Right click and select HTML element properties.
Select the HTML tab in Custom event handlers.
Select the onmouseover event from the drop down, then add some code:
alert("Hello!");
Run the form and hover the mouse over the button. Voila!