Shiva, I have absolutely no idea if this can be done, but Jonathan Drummey (a Tableau Zen Master) just did a Webex on Grand Totals today. Here's the link: http://community.tableau.com/message/209971#209971
You might find your answer there. If not maybe Jonathan will take an interest.
I don't know of any way to use a Grand Total computation in further calculations. However, with table calculations we can compute the same results as a grand total computation and use those in futher calculations. The webex that Shawn linked to talks about exactly that.
Beyond that, I'm not able to help right now. Your data is not in a usable format for Tableau nor do I know how you'd want it to be laid out or what the total would be computed over. If you need more help with this, please provide a packaged workbook with some sample data and a mock-up of what you'd like.
Hi Shawn & Jonathan,
Thanks for reply.I should fallow the table calculations.