Handls can not move,How to fixed it

Unity Engine
1

Hi all,
I want to drag one gameobject on OnSceneGUI(),but not work,How to fixed it?

mpolyObj.movePoint.transform.position=Handles.Slider(mpolyObj.movePoint.transform.position, Vector3.left);

1849998--118648--slidebug.jpg
1849998--118648--slidebug.jpg1076×437 70.7 KB

2

any body can help?thanks in advanced~