Final answer:
To manually add 'cannot' criteria to a form, one would need to implement scripting or programming rules that enforce these conditions during user input, likely using a client-side language like JavaScript.
Step-by-step explanation:
The question pertains to modifying a form to include certain criteria, likely for validation or specifying the behavior of the form elements. This often involves programming or scripting to ensure that the form behaves as intended when user input is involved. For example, to add a user cannot criteria, you might need to add a script or a set of rules that validate the input fields to prevent specific values from being entered or accepted by the form.
These criteria could include conditions like not allowing certain email addresses, usernames, or ensuring that text fields do not contain specific keywords that are not permitted. In many cases, this would involve adding JavaScript or another client-side scripting language to handle the logic on the form directly within the webpage's HTML.