Scripting is a very powerful way to apply the effect of a feat. This is an advanced feature however – creating new feat scripts requires at least basic knowledge in programming. If you only want to edit the scripts (for example change a bonus from +4 to +6), you don't need to learn to program, just change the values at the correct places.
If you wish to create a new routine, use an existing feat as a starting point if possible. Be careful and save often if you are not sure of what you are doing. A poorly written script could mess with your character's stats, and cause errors while using the program.
The scripting language is VBScript, a subset of Visual Basic. VBScript is quite simple and you do not need to be a programmer to write a little code. If you know any version of Basic you will be able to program in VBScript. If you know another programming language like C/C++ or Java, you will need to familiarize yourself with the syntax of Basic first, but as the name implies, Basic is pretty easy to learn. Here are some useful links for learning VB/VBScript:
Scripting for Feats details how to code the effects of feats.
Scripting – General Functions Available summarizes functions available in VBScript
Scripting – Debugging gives tips on debugging script code.
func - Object Information lists members of the func object, which is accessible from all scripting areas.
Creature - Object Information lists members and functions of the creature object (usually Cr)
Race - Object Information lists members in the race object (usually cRace)
Attack - Object Information lists members in the attack object (usually cAtt)
LastDamage - Object Information allows you to modify attack rolls.
Item - Object Information lists the properties of items you can read/modify.
Scripting – Item Scripting explains how to add script code to items.
Skill - Object Information explains how to modify a skill's data.
Spell - Object Information explains how to modify a spell or psionic power's data.
Feat - Object Information explains how to modify a feat's data.
Bulk Data Entry shows how to use scripting to enter many feats, skills, spells or items at once.