; вариант #1
*$Space::
   While GetKeyState("Space", "P")
   {
      Send, {Space}
      Sleep, 10
   }
   Return

; вариант #2
*$Space::
1:
   If !GetKeyState("Space", "P")
      Return
   Send, {Space}
   Sleep, 10
   Gosub, 1

; вариант #2.1
*$Space::
1:
   Send, {Space}
   Sleep, % !GetKeyState("Space", "P") ? 10:-1
   Gosub, % !GetKeyState("Space", "P") ? "2":"1"
2:
   Return

; вариант #3
*$Space::SetTimer, Action, 10
Space Up::SetTimer, Action, Off
Action:
   Send, {Space}
   Return

; вариант #4
*$Space::
   Loop
   {
      Send, {Space}
      Sleep, 10
      If !GetKeyState("Space", "P")
         Break
   }
   Return