Texture Env Mode !!!!

If by "level" you mean a stage in the texture combiners, then no, you cannot have a combiner without a textre. Not having a texture to a stage disables that stage. But you can bind any texture and then just pass through whatever you want to. You must have a texture bound and enabled, but you don't have to sample from it.

How the modulation works in that case depends entirely on how you set up the combiners. It will multiply two sources, and you decide what the sources are.