Service not finding external drive

[normvcr]

I am running

Linux 3.5.0-2.fc17.i686.PAE #1 SMP Mon Jul 30 15:18:54 UTC 2012 i686 i686 i386 GNU/Linux

and one of my services (backuppc) fails to load at boot, even though I had previously done

systemctl enable backuppc.service

but does load fine manually after boot:

systemctl start backuppc.service

Sometimes in the system log I see a message from boot-time that the service has failed to access a particular network drive (which the service does need access to).

Is there a way to delay the service trying to do its thing at boot-time until the network drive has been mounted?