[Therion] Overlay grid over maps

Good day everyone, I am in the process of remapping a large cave in which there are various archaeological / paleontological excavation areas. In one chamber of the cave an excavation grid has been setup. The excavation grid's north is 23 degrees east of true north. Magnetic north is 18 degrees west of true north. So if I put "grid bottom" into my layout I get a grid on my pdf output which is oriented to magnetic north. Is there a way to orientate this grid to 23 degrees east of true north? Thanks, Steven