File : User Preference : Check User Defined Hard Key : Create Macro on the button

That's in stand alone editor, CCP not sure but I believe you have to create that macro elsewhere and hide it if you wish, copy it to clipboard and then paste action on the button.

Otherwise if the system is that simple you could place that macro on the ON hard button to accomplish the same thing. I typically have Watch Page : On button setup to configure system for most used source anyway (usually cable or sat) but do not perform a page jump. That way the client can at least see/hear something happening on screen/speakers if they press the ON button. I'd really prefer there to not be an ON button at all.