How to work with Null and Not Null Vales

Hello Everyone,

Please help with the following:

Column A ReturnDate

Column B Closed

I want to run a formula in Column "B" which will find in Column "A"

Null Value = False
Not Null Values = True




This will be imported into a database...its a check box. about 15K rows/records.

Thanks for your time in advance,

Frank.