Meh, I got curious. What it should look like is something like this:
Custom SQL alert
using the Nodes table
(in the box where you put your code):
where nodes.nodeid = 1 (just so you don't kick this trigger for every node in the database)
and convert(varchar(10), GETDATE(), 108) >= '10:00:00'
and convert(varchar(10), GETDATE(), 108) <= '10:11:00'
This will return ONE row only between 10:00 and 10:10. Your reset would just be
and convert(varchar(10), GETDATE(), 108) > '10:11:00'
That would kick an alert once a day at 10:00.