Abstract: A one-trip assembly that includes the mill or mills for milling a window, the whipstock, the whipstock anchor or packer, and a valving assembly is disclosed which permits running in all the equipment needed for setting and orienting a whipstock and squeezing cement below the whipstock in one trip. Valving is provided which allows for the squeezing to go on after the whipstock packer is set. A feedback technique to determine that the milling assembly been pulled away from the cementing tube is incorporated into the assembly. In one embodiment, upon initiation of milling, pressure differential is used to shift a tube for valve actuation, effectively isolating the squeezed formation from pressures above the whipstock. In another embodiment, the whipstock is shifted to actuate an upper flapper. A second flapper valve is provided, preferably below the whipstock packer, which, responsive to pressure from below, is urged into a closed position.