I'm not sure you can. DateDiff("yyyy", ....) just returns the difference in the year values (ie. December 31, 1941 and January 1, 2006 are 65 years apart).

You'd be better to use the equivalent of the Excel formula:

=Date(Year(A1)+65,Month(A1),Day(A1)) and check to see if this is greater than or equal to the date in B1. It even works for leap years. :-)

Scott