PN:disabling subfunction for lease edit button in PN_leases screen

For our customer we want to disable the lease edit button for certain responsibilities, allowing them only to make amendments. We can not find the proper syntax for this subfunction however. How can we disable this button?
Below is taken from the property manager implementation guide, section C-1.

• Subfunction: A subfunction is a subset of a form's functionality. In other words, a subfunction is a function executed from within a form.

  Subfunctions are often associated with buttons or other graphical elements on forms. For example, in the Leases window, you may want to restrict access to the Amend Lease function. In this case, for all users that do not have the associated subfunction name assigned to their responsibility, the Amend button would not appear.