bind and dynamic updates

i have zones in my BIND server that are updated dynamically by some windows DHCP servers, quite frequently. however, i need to add records "manually" in these zones. can i still manually update these zones by simply editing them (using vi on my bind server like i do for the others not supporting updates), adding the record, updating the serial and reloading the thing ? (rndc reload) what happens if, during my serial update, an update is done at the same time by any dynamic system (DHCP in my case). thanks