Basicly it isnt in the Dvars thread, its in another thread you create, you can call it "KnifeKilled" without the "". Im not sure if this is the right command, but you have to put something like this:
self waittill ( "knife_kill" ); \\not sure if this is the right code, but in a thread it should look like this:
self waittill ( "knife_kill" ); \\then the code that happens after the knife kill after it.
Im sure CrazyApple will fix my "waittill" command shortly :P