Since the scheduling schedule is set by a site/project administrator, I don't think there is a way to allow users on a dashboard to do this. Instead, there are two primary options:
-Increase the current extract schedule so it happens more frequently, and add a time stamp so all users know when the data has last been updated. One additional extract a day shouldn't put too much of a load on a database or whatever your data source is, and I've found that typically 2x a day is more than sufficient, even for very needy projects.
-In the cases where immediate data is needed, opt for a live connection. This way, when the user hits the "refresh" button on the top of the dashboard, the data will refresh with the most current data. Obviously this is limited by the size and type of your data though.
I've used both of these methods in the past, so hopefully you can find a solution that will help everyone!