Number Format And Duplicates Check

I am trying to improve my expense report template and need to check on the load if expense report number has been loaded correctly as well as if this report has been previously loaded. Expense report number format looks like this: AAA-BBBBBB-CC
Where:

AAA � Employee ID #
BBBBBB � End of the week date

CC � Weekly expense report number
For instance, 023-122008-01 means: Employee number 023, week ending date 12/20/2008, weekly expense report number 01. I would like to prevent/give warning of loading incorrect expense report number format, check for possible duplicates, and check if trying to load expense report belongs to the right person (by simply matching previously loaded in different cell of the same sheet employee ID and first three digits of just loaded expense report number. I think I know how to do all of these separate, but have no idea how to combine all three checks for one cell.