Simulate button held down

My cable box (Foxtel iQ3/Pace) has a couple of functions that work by holding down the button on the remote (i.e. hold Play = Slow, hold FWD = jump to end).

Any idea how to imitate this on HR? I messed around with repeat intervals, but could not make it work. On a previous product I set the repeat interval to zero, but not having the same luck getting it to work on HR.

Appreciate any guidance.