I'm trying to extend my display to three monitors (not using a laptop; this is just my Tower/CPU). I have one monitor (a Dell P2210) connected via displayport and then the remaining 2 (a Dell P2210 and P2422H) connected via a displayport splitter. I don't have a third displayport input.

I can see my desktop on all 3 but can only move my mouse over 2 (the P2210 and P2422H via the splitter). Is there anyway to extend the desktop further so I can use all 3?