Simple regen ring mod request

[beck11]

Hi, I was wondering if any one could make me a simple ring that regens HP but only after a certain amount of percentage of the players total HP has been lost.

 

An example:

Hp regen at 5 points per sec(condition: Player Hp <20% of total HP[Regen effect stop at 99% of total HP])

 

So that means the regen effect is not constant but only kicks in at 20% remaining health. Also the regen effect needs to stop at 99% so that the ring does not keep healing me and end up becoming a normal regen ring. No need to use fancy ring models, just use any vanilla ring from the game will be fine. Idk if this is actually possible without OBSE and scripting but I hope somebody can do this simple request for me. Thx in advance.