As far as im aware movement points can only be spent in your activation unless it specifically says interrupt?

So opportunistic is used when you cause damage to gain a few movement points, but can it be used when the enemy hits you to then back off? Didn't think it could but got told otherwise today.

Same as any other gain movement points ability i guess, am i wrong?

P.S. Opportunistic reads:

Any merc Figure

Use after a hostile figure suffers damage. You gain 3 movement points.

edit: Damit, found it in the rule ref.

where has the delete post button gone

So, you found that receiving movement points out of your activation must be spent immediately (as an interrupt) or they are lost.

In the core RRG, it's on the next page, at the end of the Movement section, with nothing to indicate that the section hasn't ended. Caused lots of trouble for our group