Here you go almost straight out the manual.

Code:
if(!mov_targetlock)
{
mov_rotdir.pan = -mouse_force.x;
}
else
{
vec_set(vectemp,det_last_target.x); 
vec_sub(vectemp,my.x);
vec_to_angle(my.pan,vector(vectemp.x,vectemp.y,0));		
}