I was thinking on a way to cast haste on an enemy, and then stop concentrating on the spell in the enemy's turn (no action required). The idea is to make the enemy waste 2 turns.

The spell needs a willing target, so we need to "convince" him that he wants that spell.

My ideas so far:
With spells like *charm person, mass suggestion*.
With spells that have concentration like *dominate person, suggestion*. I don't know how concentration will work in this scenario.
*Bluffing* the target. A lot of DM fiat here.

Will these ideas work? Are there more ways that the ones I've thought?