Weapon Proficiency/focus/specialization as a prereq

[Illvatar]

I'm looking to setup several feats that require specific prerequisites, as indicated in the title. I know, for instance, that I can check for weapon focus in general with "tagis[WepFocus.?]", but I will need to check proficiency, focus, and specialization for specific weapons. Does anyone know how I can do this?

Thanks,
Illvatar