If you have a Renishaw RMI-Q interface on your mill, there are macros available on Renishaw's website for free download to allow you to pair/un-pair the probes. Attached is a port of that macro to LinuxCNC that I use on my mill.
It expects the probe start pin on the RMI-Q to be connected to the motion.digital-out-XX pin in your HAL. The motion.digital-out pin number is configurable. The macro takes two parameters, the first is the probe number (1 to 4) and the second is the operation. An operation value of 1 starts pairing the selected channel, 2 un-pairs the selected channel, and 3 un-pairs all channels.