Dim P() As String = Split(TextBox1.Text, "+")
Dim Soma As Double = 0
Dim i As Integer = 0
For i = 0 To UBound(P)
ListBox1.Items.Add(P(i))
Soma = Soma + CDbl(P(i))
Next
ListBox1.Items.Add("------")
ListBox1.Items.Add(Soma)