Workflow 7.5 CheckBox onclick event question

Hi all:

I'm working on Workflow 7.5, and I'm trying to check the onclick event on a CheckBox.

The simplest test I can imagine is to show an alert window when the event fires, but I'm not able to get this to work.

In my web form, I have a CheckBox with Functionality tab > Control ID = ChkBoxTest1.

In Functionality tab > Custom Events I have an onclick event with the following code:

window.alert('Onclick event');

When I run the workflow, I cannot get the window alert to appear when I click on the checkbox.

If I create a DropDownList and I assign the same code to the onpropertychange event and it works properly.

Am I missing any step?

Thanks in advance:

            Falquian