CheckedListBox1 項目數值相加

本題要達到上面圖示內容(是數值)相加,程式如下:
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim addsum As Integer = 0
For i As Integer = 0 To CheckedListBox1.CheckedItems.Count - 1
addsum += Val(CheckedListBox1.CheckedItems.Item(i).ToString)
Next
MessageBox.Show(addsum)
End Sub
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
CheckedListBox1.Items.Add("4")
CheckedListBox1.Items.Add("8")
CheckedListBox1.Items.Add("16")
CheckedListBox1.Items.Add("32")
CheckedListBox1.Items.Add("64")
End Sub
End Class