Handling many dropdown in a page

Question

I have a page which have many dropdown..If a user changes the values of 'n' number of dropdown ,and then he clicks save button..a dialog box should appear which should give the message that 'n' no. of dropdown has been changed..
My drop-down list is this-
<asp:DropDownList id="dd" runat="server" Width="87px" Font-Size="XX-Small"  >
<asp:ListItem Value="Pending">Pending</asp:ListItem>
<asp:ListItem Value="Yes">Yes</asp:ListItem>
<asp:ListItem Value="No">No</asp:ListItem>
</asp:DropDownList>
Save button is this-
<asp:imagebutton id="btnSaveChanges" runat="server" ImageUrl="images/save.gif" ImageAlign="Bottom" ></asp:imagebutton>
<asp:Label id="SaveData" runat="server" >Save Changes</asp:Label>