I agree with AHicks above. You may be able to find a compatible programmable controller but fitting it to the bike will take a lot of work.
The PAS speeds on my bike aren't programmable either. Instead, I use this cruise control device which clips onto the twist throttle:
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It holds the throttle at any speed you choose. You then pedal to assist the bike rather than it assisting you. You can apply as much or as little pedal effort as you want. I find it actually improves range by eliminating current surges caused by variations in pedal pressure when using PAS.