How do I loop through a multi-column listbox in WPF?

Hello Experts,

I am a beginner with WPF. I fear this may sound like a silly question.

I have a listbox with two columns. Each listbox item contains a horizontal stacked panel which in turn contains textblocks.

The listbox is empty, with each listbox item being added by the end-user through a couple of textboxes placed elsewhere. The first column accepts strings, and the second column accepts only percentages.

(I have attached a relevant portion of the event sub where a user is adding new rows.)

I would like to be able to check every time the above event is fired that the column of percentages does not exceed 100%. I have a couple of labels below the listbox itself where I would like to show the running total and the remainder. However, how can I loop through the second column of percentages to show the running total and remainder?

I would appreciate any sort of guidance towards a solution on this. Thank you very much.

Private Sub btnAddItem_Click(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles btnAddSplit.Click

...

            Dim ListBoxItemName As New TextBlock
            ListBoxItemName.Text = Name.Text
            ListBoxItemName.Width = 170

            Dim ListBoxItemValue As New TextBlock
            ListBoxItemValue.Text = SplitValue.Text
            ListBoxItemValue.Width = 70

            Dim ListBoxStackPanel As New StackPanel
            ListBoxStackPanel.Orientation = Orientation.Horizontal
            ListBoxStackPanel.Children.Add(ListBoxItemName)
            ListBoxStackPanel.Children.Add(ListBoxItemValue)

            Dim NewEntry As New ListBoxItem
            NewEntry.Content = ListBoxStackPanel

            MyListBox.Items.Add(NewEntry)

...

    End Sub

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