I am having trouble getting this formula to work. I need it to calculate 28 days from column one and insert the date in column two, and if no date exists in column one the second column should be blank, any help would be greatly appreciated guys, tha...

I have two columns when a date is inserted in the first column the second column adds 20 days and populates a date which is fine, however I keep getting an error in the second column when a date in the first column has not been entered, what do I nee...