AFAIK this is not possible using the bounce function. Normally, any fader movements would already be recorded into the mix using automation. That in fact is widely regarded as one of the key advantages of using a dAW (or automated mixing console) over the "all hands on" days of having to adjust per hand during mixdown, getting it wrong, having to start all over again....
However, if you would like to manually make adjustment during mixdown, rather than bouncing, try this:
Instead of routing everything to an output channel strip, route to a bus, set an audio channel strip's input to be from that bus, set the channel strip to record ready, press record, your mix will then be recorded and you should be able to make adjustments as you go along.
I think i get what you mean, another way is to set the track to 'latch' and play from the beginning....Logic'll record your fader movements on any channel you do this to. If you assign your faders to an external midi controller with knobs or sliders you can use these also....it bassically writes in the automation for you in real time. Then you can even adjust it within the automation tool (press the A key whilst on the arrange window)
the latch function is above the pan on the track view and says 'off' by default
edit-it also records ANYTHING else you change while you play the particular track back so change it to 'READ' after you're done....the paremeters you change (the volume) will always snap to the automation you layed down by moving the fader while its on READ