Help me out with something fairly complex? (Skills, limits, default caps, and more!)

[PK]

Okay, I've tried a lot of different things to accomplish this. In fact, I've never managed to make GCA lock up completely until now. :) So instead of posting the ridiculous builds I've tried, I'd like to just present my needs and humbly solicit advice from those more knowledgeable than I.

I need to create a set of almost-identical IQ/VH skills, but for the sake of this post I'll just focus on one. Let's call it "Path of Magic" for now. This skill doesn't have to affect anything else on the character sheet, but it has some very specific properties.

1. It cannot be learned higher than Thaumatology skill. If you have Thaumatology at 13, your maximum Path of Magic skill is 13.

2. It also cannot be learned higher than (12 + Magery) level. If you have Magery 2, your maximum Path of Magic skill is 14.

NOTE: In this GDF, Magery no longer gives a bonus to Thaumatology skill; I mention this as it's potentially relevant to #1 and #2 above.

3. It defaults to Thaumatology-6. However, your maximum default level is 12, whether you have Magery or not. In other words, if you have Thaumatology-15, you know Path of Magic-9. But if you have Thaumatology-25, you only have Path of Magic-12.

Any ideas on how I can implement all three of these restrictions? When I tried it, I think my need()s went recursive, because GCA just bricked on me. :)