Panning Textures across a plane.

[shivanangel]

Helllo,

I'm attempting to create an old school environment by creating a clouds plane to put up in my sky.

I'm perfectly capable of getting the clouds to just sit there on my plane through a texture file, however what I want to know is if I can
move the texture over the plane in a direction so that it seems like they
are moving.

Thanks,
George

P.S. Is there a way to define a set color on a texure to be transparent? So that I can have multiple cloud cover layers to give things some depth?