You can use the function in
http://www.accessmvp.com/DJSteele/Diff2Dates.html
Copy everything between Code Start and Code End and paste it into a new
module (not a class module nor a module associated with a form or report).
Do not name the module Diff2Dates when you save it: modules cannot have the
same name as functions contained within them.
Set the ControlSource for your text box to
=Diff2Dates("ymd", [DOB], Date())
(replace [DOB] with the actual name of your date of birth field)
(I assume you're trying to get the current age in years, months and days.
"years, months, and days of age from DOB to next Birthday" doesn't make
sense: months and days will always be 0 on the person's birthday!)
