You need to convert the list box or label values into numeric format before you can multiply them.
When you get the result, you need to put it back into a control as text.
The TryParse method is the most suitable becasue it provides a check that the values can be converted to numbers. I am assuming that you want to multiple the contents of ListBox1.SelectedItem by Label1 and place the result in Label2. The numbers will be handled as Double.
Dim N1 As Double
Dim N2 As Double
If Double.TryParse(ListBox1.SelectedItem.ToString, N1) AndAlso Double.TryParse(Label1.Text, N2) Then
Dim Result As Double = N1 * N2
Label2.Text = Result.ToString
End If
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