What do you mean by transform?
I need that the result of a report becomes the input for another report; is it possible?
No, there is an idea on the forums for just that: http://community.tableau.com/ideas/1604
You are limited to right clicking a measure cell, select all, copy, paste to excel, then use that as a new source. You can also do worksheet, data, export as well.
There could be ways with table calcs to replicate values you need as well in the new table.