Heh, it just takes time.
To create your texture, open a default blend and delete the cube.
[>] Select the camera and press NK1, then press Ctrl-Alt-NK0. Press NK1 again. You may also have to press NK5 to get back to orthographic mode.
[>] Press F10 and set the camera image resolution to something appropriately long and thin (like 800 by 100 or something that has roughly the same ratio as your text). Also, now is a good time to select an appropriate output format, such as AVI RAW or something. Avoid anything with lossy compression such as AVI JPG.
[>] Press Space --> Add Mesh --> Plane.
[>] Press F5 for the Material Buttons. Add a new material to the plane. Set the RGB sliders to 0.0 (pure black). Click ‘Shadeless’.
[>] Click the little ‘earth’ button on the far left for the World Buttons. Set the Horizon RGB sliders to 1.0 (pure white).
[>] Scale the plane to 20 times its size.
[>] Press NK0 to get back to camera view.
[>] Press G and move the plane to the left until just past the edge of the outer-most dotted line.
[>] Press I --> Loc. This adds a location key.
[>] Change the animation frame number to the number of frames you want it to take to have a wipe across the text, plus one. For example, if you want it to take one second at 25 fps, change the frame number to 26 (25 + 1).
[>] Press G again and move the plane until it just passes the right-most dotted line (so that the entire camera view inside the dotted lines is black).
[>] Press I --> Loc again.
Now to render.
[>] Press F10 and set the end frame number to the same number you used above (my example was 26).
[>] Click ANIM.
This will give you a nice, hard-edged, “wipe” animation to use as a texture.
You can soften the edge if you have a nice alpha texture to apply to the plane in addition to the color, to blend into blackness…
To apply the texture, load your scene, select your text, add a new Texture in the Materials Buttons as usual, and in the Texture Buttons just load the AVI or MOV you just created instead of a regular image file (such as JPG, TGA, etc.). You can tweak how the movie texture is used with the Anim and Movie panel on the right.
Make sure to click ‘Calc Alpha’. Back in the Materials Buttons, the Map To should have only the Alpha clicked.
Hope this helps and Good luck.