How to do invoke validation rules in a web control from aspx modal popup

Hi,
I am working a bug where a webcontrol display validation rules for missing required fields. In another aspx form, the control is used and has a creat button with the following rules.
  <asp:ValidationSummary runat="server" ID="valSumParty" ShowModelStateErrors="False" DisplayMode="BulletList" ForeColor="red" ValidationGroup="AddParty" HeaderText="Errors"/>  <div style="text-align: right; padding: 20px 20px 10px 0;">   <asp:Button ID="btnAddParty" OnClick="btnCreate_Click" ValidationGroup="AddParty" runat="server" Text="Create" />   <asp:Button ID="btnClear" runat="server" CausesValidation="false" Text="Clear Form" OnClick="btnClearForm_Click" />  </div>  <div style="float: left; vertical-align: baseli ...