I tried using this post here: Using global keyboard hook (WH_KEYBOARD_LL) in WPF / C# And i have this sucessfully working.
But there is something i cant get my finger be
Some time ago I relied on the RegisterHotKey function and the result was pretty good. I used this in VB.NET and just for combinations of CTRL/SHIFT/ALT + letter or number, but here you have a pretty detailed C# code allowing even more combinations.