Cat 428b hydraulic auxillary spool valve

Hi' I need to install a spool valve and lines to operate a hydraulic post hole digger on my Cat 428b , Is there a facility to connect a spool valve to the main hydraulic control valve set up both for pressure and return to tank, or would it be simpler to connect directly to the pump via a tee piece and like wise to the return line at the bottom of the tank?
Any Ideas would be welcomed.
Regard's

Cat 428b hydraulic auxillary spool valve