sum using Listbox after show result in Texbox

Hi how sum using Listbox after show result in Texbox?

Function SomaListBox() As Variant

Dim resultado As Double
Dim x As Integer

For x = 0 To ListBox1.ListCount - 1
resultado = resultado + Val(ListBox1.List(x))
Next
TextBox1 = Format(resultado, "hh:mm")

End Function

imagine values
12:36
11:24
2:13
3:23
4:56
5:01
6:00
7:00
8:19

Result correct: 60:52 (h:m)

My code show icorrect result: 00:00
Thank you!