Definizione delle varie variabili nella classe principale:

codice:

    Dim itm_ As ListViewItem
    Dim itm As ListViewItem
    Dim itm2 As ListViewItem
    Dim itm3 As ListViewItem
    Dim itm4 As ListViewItem

    Dim list1 As ListViewItem
    Dim list2 As ListViewItem
    Dim list3 As ListViewItem

    Dim str(5) As String
    Dim str2(5) As String
    Dim str3(5) As String
    Dim str4(5) As String

    Dim prezzo As String
    Dim costofinale As Integer

    Dim number As Integer
    Dim number2 As Integer
Questo è il codice del pulsante aggiungi:

codice:
  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Select Case number

            Case 1

                itm_ = ListView1.SelectedItems(0)
                itm_.Remove()

                list1 = ListView5.Items.Add(str(0))
                list1.SubItems.Add((str(1)))
                list1.SubItems.Add(NumericUpDown1.Value)

            Case 2

                itm2 = ListView2.SelectedItems(0)
                itm2.Remove()
                list2 = ListView5.Items.Add(str2(0))
                list2.SubItems.Add((str2(1)))
                list2.SubItems.Add(NumericUpDown1.Value)

            Case 3

                itm3 = ListView3.SelectedItems(0)
                itm3.Remove()
                list3 = ListView5.Items.Add(str3(0))
                list3.SubItems.Add((str3(1)))
                list3.SubItems.Add(NumericUpDown1.Value)

        End Select

        costofinale += ListView5.SelectedItems(0).SubItems(1).Text
        TextBox1.Text = costofinale
Codice con cui carico il file txt contenenti i vari items:

codice:
 Private Sub LoadList(ByVal lst As ListView, ByVal lst2 As ListView, ByVal lst3 As ListView, ByVal file As String) 'carica la lista dello shop

        On Error GoTo err



        Dim a As String
        Dim b As String
        Dim c As String
        Dim d As String
        Dim e As String
        Dim f As String


        FileOpen(1, file, OpenMode.Input)

        While Not EOF(1)

            Input(1, a) 'legge dal file
            Input(1, b)
            Input(1, c)
            Input(1, d)
            Input(1, e)
            Input(1, f)

            str(0) = a ' costruzioni
            str(1) = b ' prezzo costruzioni


            str2(0) = c ' hardware 
            str2(1) = d ' prezzo hardware


            str3(0) = e ' engine
            str3(1) = f ' prezzo engine

            itm_ = New ListViewItem(str)
            ListView1.Items.Add(itm_)

            itm2 = New ListViewItem(str2)
            ListView2.Items.Add(itm2)

            itm3 = New ListViewItem(str3)
            ListView3.Items.Add(itm3)

        End While

        FileClose(1)

        Exit Sub
err:
        MsgBox("Error: shop data, can't load settings", MsgBoxStyle.Critical)

    End Sub
Codice con cui richiamo i vari Case del pulsante aggiungi

codice:
    Private Sub ListView1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListView1.SelectedIndexChanged

        number = 1

    End Sub

    Private Sub ListView2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListView2.SelectedIndexChanged

        number = 2

    End Sub

    Private Sub ListView3_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListView3.SelectedIndexChanged

        number = 3

    End Sub