Hi Ria -
As I understand it you're trying to get the % difference of each colored bar compared to the previous value? So as an example if the Clinic Activity for 1/31/16 is 0.15 and for 2/29/16 it is 0.06 then the % difference should be -60% = (0.06 - 0.15)/0.15. If so then adding the table calculations as detail on the marks card for each should give you the values for each of desired measure.
Hi Ann, Yes, you can answer this question in the manner you give, definitely. However, I was looking for just ONE line in the tooltip that dynamically populated for the measure value depending on which bar you hovered over. This, unfortunately, isn't easily doable and requires a workaround of adding a dataset to be used as a proxy dimension. I got a response from Tableau support with that workaround. In order to do this in a more straightforward fashion, here is the proposed Tableau update that allows for table calcs on the measure values field. You can upvote this addition here: https://community.tableau.com/ideas/1256