Option Explicit
Private NonUserChanged As Boolean

Private Sub fdCellularPhone1_Change()

PhoneChange fdCellularPhone1

End Sub
Private Sub PhoneChange(Field As TextBox)

Dim l As Integer
If NonUserChanged Then Exit Sub
l = Field.SelStart
NonUserChanged = True
Field.Text = FormatAsPhone(Field.Text, l)
NonUserChanged = False
Field.SelStart = l

End Sub

Public Function FormatAsPhone(ByVal Str As String, Optional ByRef Cursor As Integer = 0) As String

Dim i As Integer, k As String
k = ""
For i = 1 To Len(Str)
  If Mid$(Str, i, 1) Like "[0-9]" Then
    k = k + Mid$(Str, i, 1)
  Else
    Cursor = Cursor - 1
  End If
Next

i = Len(k)
If i > 0 Then FormatAsPhone = Mid$(k, 1, 3): Cursor = Cursor + 1
If i > 3 Then FormatAsPhone = FormatAsPhone + "." + Mid$(k, 4, 3): Cursor = Cursor + 2
If i > 6 Then FormatAsPhone = FormatAsPhone + "." + Mid$(k, 7, 4): Cursor = Cursor + 1

If i > 0 Then FormatAsPhone = Mid$(k, 1, 2): Cursor = Cursor + 1
If i > 1 Then FormatAsPhone = FormatAsPhone + "." + Mid$(k, 3, 2): Cursor = Cursor + 1
If i > 3 Then FormatAsPhone = FormatAsPhone + "." + Mid$(k, 5, 4): Cursor = Cursor + 1