Removing an text input's value right before submit event

Removing an text input's value right before submit event


Hi,
I have ASP.net control and i want to remove its value (if it has a
specified value) before submit event so server will recognize it as a
empty textbox. normally it behaves like watermark textbox. because of
that it also sends the watermark value if no text written. what should
i do?
Thanks,
Deniz