How to make a form submit button nofollow?

Does anyone know how or if it is even possible to make a submit button for a form nofollow? I have the following code for the submit button and would like the search engines not follow the path. I am pretty sure I have seen a nofollow button before but am not sure where.

<input type="submit" name="submit" value="Submit" />

PHP:

 

There is no path to follow in forms. No need for the nofollow.