I don't think VMWare has this capability in configuring alarms...at least in VC 2.0.x. Perhaps something to suggest for future VC releases? I have alarms set up, and when running maintenance mode, I get the same alerts, but disregard as I know I am working on the gear at that time. It would be nice to have a setting to ignore alarms if the host is is maint mode.
The only thing I can suggest is editing and disabling the alarm before maintenance is done. Just remember to re-enable when finished