Problems with Update Record behavior

I am sorry to ask this question again since I have not resolved the issue yet.

When I am using the Dreamweaver Update Record behavior,  I am not able to get the form validation to work.  I implemented the form validation by inserting  onsubmit="return someFormValidation(this);" into the update form created by Dreamweaver.

When I hit the submit button the JavaScript validation function is not even invoked.

However when I use the same method for form validation with Insert Record behavior I have no problems.  Is this difference I am observing between the Insert and Update behaviors the way Dreamweaver supposed to work?  If yes how can I do my form validation during an Update Record?

Note that the pages involved are all php pages, therefore we are talking about server side validation here.

If anyone can help I will be grateful as I am really stuck...