Object1.X + (object2.X - Object1.X) * 0.5
Object1.Y + (object2.Y - Object1.Y) * 0.5
Here's an old cap I did with everything stripped away apart from this feature..
object 2 is the mouse.
Changing '0.5' to a variable means you can adjust the distance.. so holding down space changes the number to 0.5 from 0.3
Oh and If you want a smoother scrolling, make a separate marker object and have it move at angle.. with the speed in accordance to the distance between itself and the position written above.
I did do one for magnification also but I can't find it..
But I do remember it was a bit of a pain to do mouselook with magnification, because zooming out would cause the mouse to be recognised even further away and it got really sensitive the further the mouse got.