to make the objects meet at the point where the mouse was clicked, you must force the sine function to be an integer number of half-waves along the vector your red object follows, from its beginning point to the point where the mouse was clicked.
here... in your update method change the frequency to this:
... where n is the integer number of half-wavelengths you want the white object to oscillate through until it intercepts the red object. I hope this is what you were after.
here... in your update method change the frequency to this:
Local frequency:Float = n*180/dist_target
... where n is the integer number of half-wavelengths you want the white object to oscillate through until it intercepts the red object. I hope this is what you were after.