I think its been mentioned that the best way to have two screens populating data on these things is to build two and tie them to the same inputs.
In theory, with one more pin to switch power between the two LCDs, or the enable, you could add code to send one screen full of data with the enable on for one LCD, then another screen with the other enable on. The LCD holds its data displayed until another enable pulse goes in so while updating one, the other wouldn't change display. I dunno if there's enough codespace left for that though.