Hi Aherin! I think this is do-able and I believe using some counter is part of the solution.  Unfortunately skill-tweaking isn't my strong suit either

Let's hope Gyt or Twinkle drop by to give you some tips.

Meanwhile there's a great series of tutorials about particles in the wiki (starting with this one) by OedipuTex.  Hopefully one of these can give you more useful info.

yea this is hard/impossible, i actually tried doing it once but couldn't find a solution..
the thing is, as gyt said there is no reference stat to trace the amount of shield your character currently has.
ive tried experimenting with
L"SHIELD ARMOR", //KSTATLOOKUP_CHARACTER_SHIELD_ARMOR
but i think that's a remnant stat from the past game and is not in use for TL2 at all
that said this feature is difficult to implement strictly for the normal shield system, which is a damage absorption shield

you can instead create a shield system that's based on taking X amounts of hits, for example you can negate 10 instances of attacks, after you turn the shield on,
this would allow you to create a custom stat to count the amount of hits you've taken so that a particle pops up when you've taken the amount of hits you deem is high enough to warrant that your shield is "low"


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however i have a completely out of the box theory/solution to possibly solve your dilemma, that would be to use a summoned dummy unit that mimics all of your current defenses(%DR, armor/resists)
and is given hp equal to the amount of shield your skill gives you
 
this dummy unit would be set to stick on to your character and use the same hit box the player does
each time you are hit the dummy is also hit, diminishing its hp and your shield at the same rate, these two events are now in synchrony.

however with the dummy unit you can track its hp..
this allows us to add a passive skill which would trigger when the dummy reaches a certain % of hp, indicating to you(with particles) that its hp is low which should in theory be equivalent to your current shield value, thus giving you your warning system...

i have never tested this myself.. and actually just came up with this thought as i was typing out this post, but if you endeavor to testing this theory please give us your results, i would try this myself but as you know im very tied up for time and can only do short posts like this, im sorry i still haven't given you the tutorial post i promised in your other thread.

np, also for my last message i think i got the wrong guy sorry bout that,
that goes out to bill hartman if hes reading this thread