Hope to get some help in making feat

[Sturmrider]

Hi all,

I am trying to make an old 3.5 feat that the players in our group insist on using. It is Spellcasting Prodigy now I have no issue with the text, level etc. the problem is I think I need an eval script to determine if the caster is INT based, Charisma based, or Wisdom based. Also if Human and can take it a second time the first thing may be to check off all the classes that can take it, but how do I put in the adjustments necessarry here is the feat and thank you for any help:

Spellcasting Prodigy
( Forgotten Realms Campaign Setting, p. 38)

[General]

You have an exceptional gift for magic.

Prerequisite
Benefit
For the purpose of determining bonus spells and the saving throw DCs of spells you cast, treat your primary spellcasting ability score (Charisma for bards and sorcerers, Wisdom for divine spellcasters, Intelligence for wizards) as 2 points higher than its actual value. If you have more than one spellcasting class, the bonus applies to only one of those classes.

Special
You may only take this feat as a 1st-level character. If you take this feat more than once (for example, if you are a human , or another type of creature that gets more than one feat at 1st level), it applies to a different spellcasting class each time. You can take this feat even if you don't have any spellcasting classes yet.