Get age as specified date given date of birth.
This is not as easy as it might seem: DateDiff("y", DOB, Date) does not work Returns Null if the DOB cannot be converted to a valid date.
Either Null or the Date of Birth as a Date or String.
The optional date at which to calculate age. Defaults to today.
GetAge ("21 Sep 1970", #1 Jan 2014#) => 44