Formatting Excel Userform textbox input into one of two specific formats

Hi, serose14,

maybe try

Private Sub txtExpressCode_Exit(ByVal Cancel As MSForms.ReturnBoolean)
Select Case Len(txtExpressCode.Text)
  Case 9
    txtExpressCode.Text = Format(txtExpressCode.Text, "84271 ##### ####")
  Case 13
    txtExpressCode.Text = Format(txtExpressCode.Text, "84271 ##### #### ####")
  Case 16, 21
  Case Else
    Cancel = True
    MsgBox "Please enter a 9 or 13 digit number"
End Select
End Sub

where my TextBox is named txtExpressCode.

Ciao,
Holger