Abstract: A straddle packer is disclosed using two inflatable packing elements mounted on a mandrel. After the packing elements are inflated, the mandrel can be moved relative to the packing elements to various positions to sample, test, treat, etc. the formation. Resilient connecting means between the mandrel and the packer require a substantial force that is detectable at the surface to move the mandrel to another position. A pin and J-slot control the movement of the mandrel relative to the packer and limit the movement so that a substantial increase in force at the surface indicates that the mandrel is properly positioned.