Yes. You could add spry validation to your new field. In Dreamweaver open the Insert Menu (Window -> Insert), click on the text field, and then select spry from the insert menu, and select Spry Validation Text field.
Note: Although this is not a common case, but this is a client side validation, so if the user have Javascript disabled on their browsers then the validation won't work.
Let me know if you have any other questions.