Ah! And I figured out the Advances. I was able to repurpose the
eval on AdvBoost to have the already-picked choices not show up. I know someone else had had this issue a while back... they probably already found their own solution.
Code:
<eval value="1" phase="Final" priority="1001">
<![CDATA[
var skills as string
foreach pick in gizmo from Skill
skills &= " & !Skill." & eachpick.idstring
nexteach
field[advDynamic].text &= skills
]]>
</eval>