Scenario: Player must travel through a cave with several bodies of fire in the way. Player can dowse the fires with a Magic Damage Frost spell to clear the way. This is made pretty obvious by the handy Icy Spear spell tome nearby. Then I thought, after thinking I had covered all options, what if the player casts a frost cloak, this "in theory" should provide some sort of protection - if the player has this spell, I don't think I will drop it nearby. So now I've added another solution to this situation, something that a player may think about and when they get toasted think "Come on! I was wearing a frost cloak." So how do I go about achieving this? First thing is I don't know how to script this, what event, if any, do I call to check if the player has a frost cloak active? When I can do a check to see if the cloak is active I can disable all damage triggers and the player will sail through the fires unharmed AS LONG as the frost cloak is active. As soon as it ends then the player must take damage from any fire he/she encounters or cast the frost cloak again and possibly again until he/she leaves the area.

Help with this please?

I love your concept. You may have to use a custom damage health spell which will be invisible (no visual/audio effects). Set the spell as "fire and forget".
Place your bodies in the location and the fire FX, then create a trigger volume that casts the custom spell by using the event OnTrigger() (no Enter or Leave).

Add checking conditions to the magic effect of the custom spell like checking if the player is NOT casting the frost cloak.

However don't forget the vanilla health regeneration spells. Magicians may want to use Grand Healing or Guardian Circle instead of Frost cloak.

This video will help explain what I have so far.
When the player hits an invisible activator inside the fire fx with a frost spell it disables the fire fx, disables the fire damage and the activator self-disables because it has collision and prevents player from sailing past. What I want is that if the player has a frost cloak active and only a frost cloak, then the damage boxes are disabled so the player moves through the fire undamaged. The invisible activator auto-disables itself when the player is in the fire and chooses not to dowse it so he/she can pass through.
So only the frost cloak will make the player immune to fire damage, any other spell, Oakflesh, Stoneflesh, etc are not a problem, player can use these to limit damage. Healing spells more than welcome. At the end of the journey the player WILL be hit by a massive fireball so hopefully they will have sufficient health to survive (there will also be a delay so player can jump away), see my other post about defaultcastontriggerscript which isn't working right now.
Video:https://onedrive.live.com/?cid=B60C11D037429D8E&id=b60c11d037429d8e%2130773&v=3