How to make a 3D text not visible from everywhere?

The question isn’t exactly here so let me try to clarify.

In my game i have the character enter a key code in order to open a door. I want the key code to be drawn onto a wall. Adding this text in 3D modelling is a bit difficult for what i need because i would have to embed 3d text into the wall (adding it as part of a texture i can’t seem to do).

Is there a way i can use 3D text and put it against the wall without it being constantly visible from everywhere?

[688-Screen+shot+2012-04-19+at+20.00.36.png|688]