How to put an object as a button or a button that appears as a tracking model

I’m trying to put for example a plane, or a cube (GameObject) with a texture, but this object have to react like a GUIButton, but my code is in c++ , how do i can make this happen???..
please help i have trayed all. but nothing works for me… :S

for example a stop(); or a play(); button to play audio.

if you want your cube to appear always on the top of everything, you have to use 2 cameras.
to see this is detail check this question I asked a while ago

and to make it react for your mouse , simply create a script(c# which is almost similar to C++) since you can write in unity either C#,javascript or Boo.
And attach the script to you box(gameobject) that will be your button.

The script should look like this:
function OnMouseDown()
{
// play your audio
}

make an another search to know better on how to play your audio file!