Slider Bar?

Hello, I am trying to create a interactive timeline with important dates on it. As the user rolls the mouse onto the interactive timeline area I would like a slider to follow their mouse. I would like a simple slider(or any graphic) to follow the mouse. The problem I am having is this slider must be fixed on a horizontal line and follow the mouse only left and right on its fixed line or plane and would prefer if it was only activated once the mouse cursor entered the timeline graphic and disabled or stops its actions once the user left the timeline. Can anybody help me out with a mouse script to do this or direct me somewhere. Thanks a bunch