In Data- Validation

Select custom enter this formula (starting in row 1 or change the 1 to
whatever row you want to start with):
=IF(ISBLANK($A1),TRUE,IF($B1$A1,TRUE,FALSE))
uncheck ignore blank.

hit ok




On Aug 8, 8:53*am, William wrote:
Coumn A has dates and blank cells.
Coumn B has dates.

Is it possible to specify that a date entered into column A must be later
than a date in Column B? *A problem arises when a cell in column A is blank,
because excel reads this as 0 and therefore ANY date in the corresponding
cell in column B is going to be perceived by excel as later and therefore not
valid. *So, in other words, what I want is a to specify that if there is a
date in column A AND a date in column B, excel will accept only a date in
column B later than the date in column A. *But if column A is blank, then
Column B will accept any date.

Thanks for assistance.
--
William