I am trying to create a formula that looks at two dates, and based on the
results places either a the calculation of number of days between the two
dates, "n/a", or "Open" as the result

Column E Column I Desired Results in Column T
1/11/2010 12/29/2009 13
1/11/2010 Blank n/a
Blank 12/30/2009 Open

Any help would be greatly appreciated. Please let me know if you need
further explanation.