I am working up a basic project tracking spreadsheet in Excel and would like to have two sheets - one which shows my active projects and one which shows my completed/cancelled/archived projects. I would like to assign each project a unique number so I know I would want to have data validation on my active sheet so that when I create a new project, and enter a project number, Excel reviews a specified range on the other sheet to see if I've used that number before. I am sure this is possible but am not sure of the logic I would need to use. Does anyone have any advice?
A branch off of this, does anyone have a suggestion as to how I could maintain these two lists of active / archived projects and maintain an incremental project numbering system in Excel?