You could just check the Owl.X against the Character.X and set it negative accordingly:
If Owl.X < Character.X then knockback = knockbackAmount
if Owl.X >= Character.X then knockback = -knockbackAmount *
The above pseudo code should give a good idea of what to do. Hope it helps and good luck with your project.
(* One note, this line has a greater than or equal to because of you only test < or > and forget the = you will introduce a bug where knock back never happens when the values are equal. You may already know this but I have seen many people forget to include the equal to in these situations so I am spelling it out just in case.)