Assuming I understand your scenario, one exchange talks to two VIPs on your F5, which then direct traffic accordingly. When doing maintenance at the lowest level (the destination) you need to cut out the middle man by stopping the VIP from processing traffic.
If you simply want to not respond at all when the VIP should be marked down, you can drop all packets under the conditions that interest you, although rejecting them would cause the exchange to fail immediately rather than waiting for a timeout, which is probably a better scenario.
if { condition indicating vip needs to be marked down } {
reject
} else{
do all other processing
}
Nimbostratus