You can use an action filter on your dashboard. On the waterfall sheet I took off your filter, and created the filter action, which inserted an Action filter on the sheet. I displayed it, and on the dashboard added it in place of the old one.
Lasso some bars, See what happens. But here's a problem. Tableau won't let me make it a multi-value slider. Only a single value slider. A multi list or multi drop-down list will work, but not the slider you wanted.
Thank you for the quick reply! The bars broken out by sub category change however, the monthly totals on either side do not. If I lasso May 2016-September 2016, I want the bar on the left to filter to May 2016 and the right to September 2016 and the change broken down by subcategory in the middle.
Is this possible?