How can I make a counter attack type event?

For example in some of my boss duals I want to do events that will cause the boss to cast a paticular spell or use a paticular item when you use a paticular spell or item...

For example: If you use a healing potion or certain spell I want the boss to counter attack with something paticular each time. How can I do this?..

Isn't there an event like Hero - Uses Item or Hero - Uses ability?
If there is, try using one of the Unit - Issue Order actions to make the boss counter it. I'm not exactly sure wether this works, but it should.