Schedule it to run per minute with CRON Schedule (*/1 * * * *)
add it to the dashboard as report (not as INLINE Search)
this will result that the report is loading even you're not watching your dashboard. keep this in mind. it's useful approach with a lot of people work with the same dashboard to avoid loading the reports multiple times. however if you have only 1 user who watches the dashboard the following one will be better for scaling in this way:
** To refresh the full dashboard every minute: **
1. open your dashboard in editing mode
2. select "edit xml"
3. modify the dashboard stanza: