Yes you can. Like Reg_Dunlop said, you can't add more UPP once the S100 is on there. So make sure you have as many layers of UPP as you want before adding any S100.
For me, it's UPPx3 for the winter, but for the warmer months, I'll just be applying UPPx1, maybe x2, then I'll top with several layers of carnauba (Pinnacle Paste Glaz). I prefer the look of layered carnauba rather than layered sealants so if the weather allows, I'll stick with carnauba.