The presently disclosed technique provides a method for operating a valve in a wellbore by: applying a first fluid pressure to a bore of the valve; trapping the first fluid pressure in a portion of the valve; reducing the pressure in the bore of the valve to a second fluid pressure thereby creating a pressure differential between the portion of the valve and the bore of the valve; and opening the valve responsive to the pressure differential. The valve may employ a first piston disposed in the body to trap a first fluid pressure in a chamber to create a differential pressure across a second piston when a second fluid pressure is applied to open the valve to fluid flow therethrough. The valve and the method may be used to actuate another valve downhole.