Motion 5 :: Link Position Of Object To Another Shape Outline Last Point Offset

I want to link the position of an object to another object like this

- Source Parameter = Object.Shape.Outline.Last Point Offset

- Apply To = Properties.Transform.Position.Y 

I make all the linkings and the result animation is wrong. I want the linked element to have the same position as the source element.The linked element totals is position with the source's position and animation is not what I want.