hmm it could be done but i wouldn't say easily..
ok here is the basic stuff:
you need to make it a skill and link to a common event and then it will go something like:
loop
-v(rand) = random(1,4)
-if v(rand)= 1 then
--show image (you will need to show say up arrow image or whateva)
--wait 10frames(half a second respone time, how bout it?)
---if button (up) is pushed then
----v(pwned) +1
----if v(pwned) >=10 then
-----v(pwned = 0
-----show animation: something
-----change hp (all enemies) - X (do whatever)
-----end loop
---else
----message: you failed to combo
----end loop
(then the same with left right and down)
repeat
once out of the loop, the skill is done, the enemies are either damaged or you failed, combo can change their status, damage them or whatever you want it "should" work
but you might want to put over half a sec reaction time
also note: the player has to keep pushing cause when the wait ends the key has to be pushed