Change number of staves in mid-piece

I am writing some choral music for soprano, alto, tenor, bass. Most is written on two staves, with two parts to each. However there is a complex section in the middle, and for clarity I'd like to expand that section (only) to four staves with one part each. I've tried making a selection, and working with the Instruments dialogue, but it changes the whole score. Is there a way I can just have this section on four staves with the rest on two?