Sherman

Option Explicit

Sub AddAge()
Dim Bday As Date
Dim ofSet As Byte

    With Sheet1

        Bday = .Range("E7").Value ' get the birth date
        ofSet = IIf(Date < DateSerial(Year(Date), Month(Bday), Day(Bday)), 1, 0) 'offset required if birthday hasn't happened this year

        If Bday <> "" Then
            .Range("E8").Value = DateDiff("yyyy", Bday, Date) - ofSet ' write the age in years to the cell
        End If

    End With
End Sub