Getting custom mouse cursor to display above GUI and default layer

In my unity game, I created a custom mouse pointer, which is a GameObject (GUITexture). I am able to manipulate other game objects with this mouse pointer (ex. highlight and select object) in the default layer. I also created a new GUI layer and GUICamera, so that my GUI controls are displayed above the default layer.

Currently I have 3 cameras and 3 layers:

1. MainCamera - depth 0, culling mask is everything except GUI layer and top layer

2. GUICamera - depth 1, culling mask is GUI layer, all GUI controls are in GUI layer

3. TopCamera - depth 2, culling mask is top layer, the only object in this layer is mouse pointer

Clear flags for both GUICamera and TopCamera are set to depth-only.

My problem is, that I cannot get the custom mouse pointer above GUI controls. Can anyone help me with this? Perhaps I overlooked something?