Speed Path

Hello all, I guess it's my turn to look for some help in general mapping. Here is the thing http://prntscr.com/nsglny
I need something very specially, trigger_push or whatever it will be, that push player straight but in the way that you can change direction to left with angle 45 degresee by holding "A" key and instantly change direction to right if you hold "D" key (again on 45 degresee). And finnaly when you go out ,that entity will just push you straight again?? Any tips,thanks ?