This seems impossible to me.
Okay, aiming at someone is good, but throwing is a different story. Shooting reaches the target at the moment you, like, well, click.
Then throwing a semtex or throwing knife, the second you threw it, the target is somewhere else already, basically you need to take traveling time into account, and it's kinda impossible for a program to know what EXACT direction the target is going to walk.
Unless god controls it, but I'm not in the mood doing that all the time (ZING! XD)