javascript and dynamic data

I'm using Dynamic Data 4 on my project. In a template field there's a button tha开发者_Go百科t modify (via javascript) the value of the databound input field. The button modify the input box value correctly but when the input field get the focus his value it's resetted to the previous value. The same happens when saving the form. If the input box previously received input from the keyboard the value it's correctly stored.

Is that behaviour to be considered normal with those premises? There's a way to avoid it?

Thank you very much.

The problem was caused by the presence of an associated asp:TextBoxWatermarkExtender who resetted the value when the (originally null) textbox got the focus.