Fortunately, SKSE (or Skyrim itself, not sure atm) does offer a function for getting input from a keyboard. The functions for doing this can be found in "Input.psc". So you could probably do sth like (sorry if it's wrong, though I'm a kinda experienced programmer, I don't have much experience with Papyrus yet):
Function SomeFunction()
RegisterForUpdate(0) ; replace 0 with the interval you want to check for pressed keys
EndFunction
Event OnUpdate()
If IsKeyPressed(0x1C) ; Do something when 'Enter' is pressed (IsKeyPressed uses DirectX scan codes)
DoSomeAwesomeStuff()
EndIf
EndEvent
