first check you schedule works r not.
if you want to refresh server data with latest then do parameter and get new data only in server,
Live connection will always get updated. if you applied date in filter check in filter.
Refresh then do some script and get it.
I tried with the live connection and made some changes in the excel data source after publishing the dashboard in to the server but it is not updated in the server.plz let me know if any changes required.
If you are using excel as a data source you need to push the latest extract using tabcmd utility. Else if you are using a Live data connection such as Salesforce or SQL server you can schedule the refresh on the server itself.
I get a feeling that you are using excel as your data source which cannot be dynamically updated using scheduled refresh. So I believe you should use tabcmd utility to push latest extracts to the server.
For more information on tabcmd please refer the following link:
Let me know if it helps.