i need to read the selected value of DropDownList from VBScript, the code is the followig, but i dont know what's the problem?

Codigo:

<asp: DropDownList ID="DropDownList1" runat="server">
<asp:ListItem>Calidad de Contenidos</asp:ListItem>
<asp:ListItem>GOD conenidos</asp:ListItem>
<asp:ListItem>Perfil Usuarios</asp:ListItem>
</asp: DropDownList>

<script language="VBScript">

Function btnpru_OnClick()

//LLamar a una funcion con el valor selecionado del DropDownList
BuildPivot(DropDownList1.SelectedItem.Text) ???????

End Function


Function BuildPivot(valor)
.....................
.....................

End Function

</script>