Create and use Variables in Filters

Use case:
I run a weekly change control board. To capture and report all the issues for review, I use a set of reports. Six of these reports require the use of the date and time of the PREVIOUS CCB. (e.g., "Issues changed since last CCB", "New issues since last CCB"). To manage this, I currently have to edit each report to update the "last CCB date".

It would be nice is there was a way to create and use a variable for such needs.