Hide unlit part of object

Support Materials and Textures
1

Hello,

I created a scene with a text and an area lamp that lights only a part of the text. I also added a background image for rendering. The result is shown below.

http://caz666.free.fr/test.jpg

But I would like to hide the part of the text that is not lit on the right to simulate the progressive apparition of the text in an animation. Is it possible to do that with Blender ?

Thanks.