Change Submit Button Text Upon Form Submission Javascript

Working on a little project and wanted one of those fancy effects where when someone fills out an email submission form, the text changes from 'Submit' to something like 'Please wait...' or 'Sending...'. A few seconds of Googling and voila: <form name="form_name" action="http://www.codeave.com/html/get.asp"><input type="submit" name="button_name" value='Submit' onClick='form_name.button_name.value="Please Wait...";return true'></form> I annotated the colors of the different fields you have to pop into the onClick statement.