Alright.
In the States menu, make a new state and in the box labeled "Attribute", the box with the checkmarks in it, make sure "No Experience Gain" is checked. Then, make a skill for this and make it so it will inflict this State on the enemy. Then, in a monster group, make an event (Note: you will have to do this for each monster. Make the trigger "Turn 0 + 1x" and make the frequency "Turn Trigger". Then, create a conditional branch, with the condition saying that "When [monster name] gets state [state name]". Then, make a Force Action under the Conditional Branch, that says "[previous monster], Escape, Random, Execute Now".
In battle, when the skill is used, the monster will get the State, and then on its next turn, it will escape (sorry I couldn't figure out how to git rid of them immediately on skill use.) Refer to the picture for more information.