Needs review
Source: Player's Handbook II

Description: You are skilled in lining up accurate, deadly shots with your crossbow.

Prerequisites: Base Attack Bonus +1, Weapon Focus (Hand, Heavy or Light Crossbow), Weapon Proficiency with (Hand, Heavy, or Light crossbow)

When using a crossbow for which you have the Weapon Focus feat, you gain a bonus on damage rolls equal to 1/2 your Dexterity bonus. If you have the skirmish or sneak attack ability, the maximum range at which you can make such attacks increases to 60 feet when you are using a crossbow for which you have the Weapon Focus feat.