Routing Alerts to different groups based on Time!

Hi,

Currently we have alerts configured in PI 7.1, so we recieve them by Group1 and Group2.

Now we want to configure rules in such a way that Group1 should recieve alerts from 9AM to 9PM only and Group2 should recieve alerts from 9PM to 9AM only.

could anyone suggest how to achieve this.

Regards,

Shiva.