Set up an extra violin staff using the instruments dialgoue. Make sure the transition to and from the divisi is on a system break. Input the music in the extra staff you've set up. Once all the notes are in, triple-click the extra staff to select all of it, and use 'hide empty staves' to get rid of it when it's not used.
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Jay Vilnai
Macbook Pro 2.4Ghz, 8GB RAM, 750GB 7200RPM HD, OS 10.7.5, Sibelius 7.1.3 and 6.2, Kontakt, Vienna Strings, too many guitars
You could use an ossia staff, reset the size in 'Add Instrument' and join up the bar-lines. Example attached. Use system breaks if desired as suggested by Jay.