You will need to assign #38 to a system speed dial and then program that speed dial bin number to a button. You can find programming system speed dial from the user guide:
From ext.10 press Redial, Speed Dial button, enter bin number (from 50 to 99), enter #38 (if it doesn't take a #, enter 4438 instead), press Redial again.
So whatever bin number you programmed #38 to, assign that to the buttons in program 39 as *XX where XX is the bin number.