When you create a snapshot you create a snapshot task which (provided you are using a server-side data store) can be run from a job. To refresh the data, run the snapshot task as part of a job. If you create a job with both the snapshot and the process that uses it, they will automatically connect and will 'stream' the data through the snapshot into the process. You can then choose whether actually to write the snapshot or not (for improved performance efficiency if you want to do straight-through processing) by either enabling or disabling the staged data bucket that the snapshot writes to. The snapshot task being in the job means the data will be refreshed.
For design work in Director, you can refresh the snapshot by re-running it manually from the right-click menu.
Thanks a Lot Mike for the quick response.