Help with a VBA condition

Hi

I have this VBA code but I would like it to not produce an error message if the TextBox is left blank.

Private Sub TextBox5_Exit(ByVal Cancel As MSForms.ReturnBoolean)
    Dim strCode
    Dim sOut As String, i As Integer
    strCode = Replace(UCase(TextBox5.Value), " ", "")
    If Not (strCode Like "[A-Z][A-Z]######[A-D]") Then
        MsgBox "Please enter NINO in the correct format", vbCritical
        Cancel = True
    
    Else
        For i = 1 To 9
            Select Case i
                Case 3, 5, 7, 9
                    sOut = sOut & " " & Mid(strCode, i, 1)
                Case Else
                    sOut = sOut & Mid(strCode, i, 1)
            End Select
        Next i
            
    End If
    TextBox5.Value = sOut

End Sub

Thanks

Don