On the PC version, if you go to the Palette controls and look for Mixers (or even under the PMS tabs) there is a percentage setting to change the Tint. It may not be perfectly controllable within the CMYK dialog, but all of the others cross-over anyway. In other words, if you were to set a color as PMS or RGB, the CMYK equivalent is there, as well. Adjusting the tint within the other controls also adjusts the CMYK settings.