Distinct animations on each of several layered textures...possible?

Is it possible to set up different IPO offset animations on layered textures within one material?

I’m essentially trying to get stacked textures to moire against one another as they both move, by setting layers to “multiply”, “difference”, etc.
Of course, I can get an IPO for ofs set up on a material, but it is applied above the textures (as seen in the outliner), so affects them all uniformly.

This is a common effect in other CG apps, but I cannot locate a tutorial on the topic.
Does anyone have any pointers? Or is it impossible to get textures animating against one another in a material’s texture stack?

p.s. - to maintain continuity with an ongoing project, I must work in 2.49b.