I have 3 date fields:

STARTDTE ENDDTE REVDTE
08/22/2007 12/15/2007 If REVDTE NULL use STARTDTE
08/22/2007 12/15/2007 09/01/2007 If REVDATE NOT NULL use REVDTE

There will always be a date in the STARTDTE & ENDDTE cells. These are the
dates to be used if REVDTE is "NULL". If REVDTE is NOT NULL (contains a date)
use this date in the calculation.

Thanks in advance
Ralph