Private Sub CommandButton1_Click()
Dim hh_5 As Double
hh_5 = CDate(TextBox1.Value)+CDate(TextBox2.Value)+ CDate(TextBox3.Value)+ CDate(TextBox4.Value)
Me.TextBox5.Value = Evaluate("=TEXT(" & Application.Substitute(CStr(hh_5), ",", ".") & " ,""[hh]:mm"")")
End Sub