Preventing the Shield spell's shader effect from overwriting another shader.

[Craddok]

So I've got a skeleton with a shader "spell" applied to it (the unused Skeleton Hero shader). It can also cast a shield spell, but the shader of that effect overwrites the skeleton hero shader for the duration of the spell (once it expires, the original shader is restored). I'd like to prevent this from happening, although I'd like to keep the shield's initial casting effect and animation (which shouldn't be a problem). Ideally, I'd also like to keep the shield's "on-strike" effect--where it momentarily glows bright whenever the caster is struck (which should be a problem, since I'm guessing that's part of the shield's shader).

 

I only discovered shaders a few days ago, so I've got no idea how to go about this. My best guess is a custom scripted spell, which is why I posted here, but I might have to create a custom shader and somehow getting a custom shield spell to use it instead of its default effect.

 

Any ideas?