BIND 9 - force secondary to update/refresh from primary

[lui at people.net.au]

We will be upgrading from BIND 8 to BIND 9, the plan is to upgrade the 
secondary name server first and do the primary later (not on the same day).

After upgrading the secondary, we want to make sure zone transfer from 
the primary (BIND 8) still works, so we will be making changes to a test 
zone in the primary name server (i.e. incrementing the serial number). 
Instead of waiting for it to happen, is it possible to force the 
secondary to update/refresh the zone without using rndc?

TIA

Peter