Multitexturing with multiple passes

I am pretty new to multitexturing and could use some help understanding a simple question about best practices for multitexturing with multiple passes: I want to use the output of the final texture unit of one pass to be the input to the first texture unit of the subsequent pass. What is the highest performance way to get this done?

Thanks for any help.

Well, it sort of can be done by rendering previous pass to the texture, then binding this texture to the first unit. Otherwise the target color buffer is available only for the blending stage.