How about this?
Create a global variable called "spacekey" or something like that. Then create an event: "on Space Key pressed" -> Set variable "spacekey" to "1-spacekey" (without quotes; and where "spacekey" is the name of your global variable; on the event sheet it should look like this: 1-spacekey.
Now create 2 new events for "Compare variable spacekey"...
on the first one: "spacekey" = 0 -> Set animation to Frame0
on the second one: "spacekey" = 1 -> Set animation to Frame1
Please let me know if this works out for you.