using the AJAX cascading DropDown.

I'm using the cascading DropDown.  I have three drop-downs and accept and cancel buttons on a WEB form.   I'm displaying the form as a model popup using JavaScript - showModalDialog.   If the user click scancel, I just call self.close().    if the user click Accept, after making selection from the three drop-downs, I need to call the server to update the database.  I could use the ASP button control for Accept and put my database in the code-behind.   However, if I do this, and I have made a selection from the first drop-down, the code-behind for the Accept button is not called.  if I do not initially select from the first drop-down, or if I select the Prompt text, then the code-behind for the Accept button gets called.  Wierd.  It's like something with the cascading DropDown is impacting the Accept button functionality.

So, I thought instead of using an ASP button, I could use an HTML button and call a WEB service from JavaScript to update my database.

Any thoughts on this?

Bottom line is this:  From a modal popup, I want the user to select from three drop-downs (cascading), and the value in the last drop-down gets recorded in a database table.