Calculate A Person's Age Not Working.

Hi all ,
I am trying to calculate a person’s age.
Went to Customer Form
Have a field called cust_birthday ( date/time ) ( 99;00;00;>LL;0; )
Have a field called cust_age ( Number )

Went to Madules / New / then add this code,

Public Function Age(dteDOB As Date, Optional SpecDate As Variant) As Integer
Dim dteBase As Date, cust_age As Date, cust_birthday As Integer
If IsMissing(SpecDate) Then
dteBase = Date
Else
dteBase = SpecDate
End If
cust_birthday = DateDiff("yyyy", dteDOB, dteBase)
cust_age = DateSerial(Year(dteBase), Month(dteDOB), Day(dteDOB))
Age = cust_birthday + (dteBase < cust_age)
End Function


Not Working get no return. Can someone help me. Thank You if you can….

John