I found a helpful link that assisted me with adding a Double Click mouse event to a listbox in C#.net and then rewrote the code in VB.net.
Here is the code snippet for the .aspx file:
<asp:ListBox ID="hiddenColumns" runat="server" ondblclick="hiddenColumns_DoubleClick()"></asp:ListBox>
<script type="text/javascript">
function hiddenColumns_DoubleClick() {
document.forms[0].hiddenHidden.value = "doubleclicked"
document.forms[0].submit()
}
</script>
<input type="hidden" name="hiddenHidden" />
And here is the code snippet for the .aspx.vb file:
If Not Request.Params("hiddenHidden") Is Nothing And Request.Params("hiddenHidden") = "doubleclicked" Then
'Desired actions here
End If