I made a ring that casts burden on you when you put it on but how can I make the burden not turn off untill you unnequip the item? (I can't do it as an enchantment because the spell is activated by a script)

the way I think more easy to implement this is making it as an ability you can add and remove to/from target
I tried imagining how this ring of yours works but give up

PS: I think I found the utility of this, that ring acts as 'normal' until something trigger its 'curse'

well... I wanted to make the one ring from lord of the rings. I wanted to make it so that when you equip the ring it gets heavier untill at last ring wraiths attack you. Also while the ring is equipped it would make you invisible also your screen would be blurry and stuff like that. could u or sumone that reads this help me accomplish that?

So you want the ring increasing the burden...
again seems the better is making several ability type spells and changing then in the scripting. Abilities are such as disease, they last until removed. If I understood this is what you are seeking. But here you need to know if the ring is equipped, easy thing if you use OBSE (but I'm a bit unsure here if mod or option as wrye bash unlimited rings and amulets may mess this check).

ok well ive been messing around with the scripts and i got the effect set as an enchantment so its all good. Thanks for the help! =]

It might be easier to just use an ability which reduces the player's encumbrance at various periods, then restores them when the ring is removed. It's a little more difficult to work with than several burden abilities, and would work by lowering the maximum that a player could carry, not increase the weight of anything they had, but might be a bit cleaner than swapping out multiple abilities.

http://cs.elderscrolls.com/constwiki/index.php/ModActorValue
http://cs.elderscrolls.com/constwiki/index.php/Encumbrance

But really though, the effect probably wouldn't be noticed by anyone since almost everyone uses a mod or something else which allows them to carry more. Even as far as burden goes, what would seriously inhibit most people (50-100) would, and is, rather meaningless when people have carry limits over 2k. This is because the spell effect just adds to the player's weight, rather than affecting it by percentage (like it was in morrowind). And there is no real way to combat this since the player may be achieving that additional carry weight because of changed game settings, having alot of strength, or through scripting.

And from a LOTR perspective, the ring didn't become heavier when used.

I agree here, maybe actuating over fatigue is even better. and much more easy to script ... don't even need define abilities or spells