Hold the Line

(Complete Warrior, page 100, DnD 3.5)

[General]

You are trained in defensive techniques against charging opponents.

Prerequisite

Combat Reflexes, base attack bonus +2

Benefit

You may make an attack of opportunity against a charging opponent who enters an area you threaten. Your attack of opportunity happens immediately before the charge attack is resolved.

Normal

You only get an attack of opportunity against a character that exits a square you threaten.