I agree here. Banking is a technique best applied by those who are already quite familiar with the processor and the tools in use. The Keil tool set does indeed support banking which works especially nicely when programming in the C51 language. There are however a number of big issues around using banking when function pointers are being used. Make sure you read all the pertinent App Notes on this subject from the Keil web site before committing to using code memory banking.
Michael Karas