3D Object Position on GUI Screen

i want to make a gui texture on a 3d world object , how can i get the 3d object's position on guiscreen

You can use the WorldToScreenPoint function.

Example : var screenPos : Vector3 = cam.WorldToScreenPoint(3dobject);

Where cam is your camera, 3dobject is the position (vector3) of your 3D object in the scene.

Hope it helps :)