Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
    a = Selection.Address
    b = InStr(a, ":")
    If b > 0 Then UserForm1.Show
End Sub

Private Sub UserForm_Initialize()
    a = Mid(1 / 7, 2, 1)
    c = Application.Sum(Selection)
    TextBox1 = Replace(c, ".", a)
    TextBox1.SelStart = 0
    TextBox1.SelLength = TextBox1.TextLength
    TextBox1.Copy
    CommandButton1.SetFocus
End Sub
Private Sub CommandButton1_Click()
    Unload UserForm1
End Sub

Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
    If Target.Count > 1 Then UserForm1.Show
End Sub