Please provide more detail about exactly what it is you're trying to achieve.
What's wrong with creating a report in Tableau connected to the Excel file and including that view in the dashboard?
I wish to have the data in the dashboard as an output view for the user
Here's an overview on how to connect to Excel in Tableau - http://www.tableau.com/learn/tutorials/on-demand/connecting-excel-csv-and-text-files
Based on your explanation I would create a view of your Excel data and add that sheet into the dashboard.