Use DropDownList to pop-up a window or re-direct after submit.

When the user selects "Home Equity Line of Credit (HELOC)" I want it to pop-up a window with links to some forms. Or I have them re-direct to that page after they hit submit.
Any ideas? Here is my drop down list.

<asp:DropDownList ID="ddLoanType" runat="server">
<asp:ListItem Selected="true">Choose one the following:</asp:ListItem>
<asp:ListItem>1st Mortgage</asp:ListItem>
<asp:ListItem>First-time Homebuyer</asp:ListItem>
<asp:ListItem>Second Mortgage</asp:ListItem>
<asp:ListItem Value="thankYouHeloc.aspx">Home Equity Line of Credit (HELOC)</asp:ListItem>
<asp:ListItem>Contruction Loan</asp:ListItem>                               ...