notifications for item summary of a host group

[oyster2008]

Hello,
Does anybody know how to set an email notification for the item summary of a host group?

For example, I have an item to monitor the qps of the machines in a host group. If at least one of the qps value exceeds 5K, send a notification about the number of hosts in the host group whose qps exceed 5K.

thanks for your help!