I put a sheet in a layout container and hid the title. This sheet will say "ERROR! YOU MUST NOT SELECT A DATE RANGE GREATER THAN 6 MONTHS!" if you select a huge date range. If you do not select a huge date range then the dashboard would run normally. It should almost be like a secret pop-up window.
Unfortunately, there is still a strip of space showing up despite the fact I DO have a layout container containing the Breakdown, Total Records, and that "hidden" sheet. When my Error sheet is "hidden" it's still adding an unnecessary 32 pixel strip to m dashboard. Yes, I can make it grey to make it less noticeable, but I don't want those 32 pixels there at all. Is there no way to make it completely collapse when empty?