How do I create a popup box for my wizard control?

I have a wizard control and am needed to create a popup box (dialog) that, depending on which option the user chooses, will either allow the code to continue to execute or stop/prevent the remaining code within the onclick event from continuing to execute. My problem is that the onfinishbuttonclick event for the wizard is already being used to do some things and I'm not sure how to work a popup dialog within the event. Any ideas or examples would be appreciated. Thank you.

current HTML

                                    <asp:Wizard ID="wzInspection" runat="server" BackColor="#EFF3FB" 
	                                    bordercolor="#B5C7DE" BorderWidth="1px" DisplaySideBar="false" 
	                                    Font-Names="Verdana" Font-Size="0.8em" Headertext="" 
	                                    Height="638px" Width="865px" onactivestepchanged="wzInspection_ActiveStepChanged" 
	                                    onfinishbuttonclick="wzInspection_FinishButtonClick" 
                                        FinishCompleteButtontext="Complete" FinishCompleteButtonStyle-ForeColor="Blue"
	                                    onnextbuttonclick="wzInspection_NextButtonClick" 
	                                    onpreviousbuttonclick="wzInspection_PreviousButtonClick"
                                        OnCancelButtonClick="wzInspection_OnCancelButtonClick"
                                        displaycancelbutton="true" 
                                        ActiveStepIndex="0" >

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current C# code

        protected void wzInspection_FinishButtonClick(object sender, WizardNavigationEventArgs e)
        {
            // this is the Complete button on the Misc step
            bool bWeGood = true;

            FinalValidation();

            if (Session["InspectionAccepted"].ToString() == "F" && Session["ReadOnly"].ToString() != "1") //SECURITY
            {
                string InspDateToUpdate = string.Empty;

                if (txtInspectionDT.Text == "")
                {
                    InspDateToUpdate = "ISPDT1";
                    txtInspectionDT.Text = ArrowGlobalFunc.convertDateToInt(DateTime.Now.ToShortDateString());
                }
                else if (txtInspectionDT2.Text == "")
                {
                    InspDateToUpdate = "ISPDT2";
                    txtInspectionDT2.Text = ArrowGlobalFunc.convertDateToInt(DateTime.Now.ToShortDateString());
                }
                else
                {
                    InspDateToUpdate = "ISPDT3";
                    txtInspectionDT3.Text = ArrowGlobalFunc.convertDateToInt(DateTime.Now.ToShortDateString());
                }

                if (saveInspection(int.Parse(Session["ActiveInspectionPage"].ToString()))) // save the items on the step
                {
                    ArrowGlobalFuncWebCtrls.saveInspection(InspDateToUpdate); // save dates

                    ////Set Dekra Approve DT to 0
                    //string sSQL = "UPDATE " + Session["Library"].ToString() + ".INSPECTION SET ISPTRSAPDT = 0 WHERE ISPNUM = " + Session["ISPNUM"].ToString();
                    //ArrowGlobalFunc.updateDB(sSQL);

                    lblSaveSuccess.Text = "The Inspection has been saved and Notification emails have been sent";
                    lblSaveSuccess.Visible = true;
                    btnAddInspection.Visible = true;
                    btnHome.Visible = true;
                    lblCompleteWarning.Visible = false;

                    wzInspection.FinishCompleteButtonStyle.CssClass = "hideme";

                    LockInspection();

                    Email smtpMail = new Email();
                    StringBuilder emailBody = new StringBuilder();
                    emailBody.Append("<b>Inspection entered or Re-inspection!</b><br><br>");
                    emailBody.Append("Vin: " + txtFullVin.Text.Trim() + "<br>");
                    emailBody.Append("Fleet: " + txtFleet.Text.Trim() + "<br>");
                    emailBody.Append("City: " + txtCity.Text.Trim() + "<br>");
                    emailBody.Append("Location: " + txtLocation.Text.Trim() + "<br>");
                    emailBody.Append("Unit: " + txtUnit.Text.Trim() + "<br>");
                    emailBody.Append("Insp Co: " + Session["uCompName"].ToString() + "<br>");
                    emailBody.Append("Inspector: " + ArrowGlobalFuncWebCtrls.GetInspectorName(int.Parse(Session["uID"].ToString())) + "<br><br>");
                    emailBody.Append("<b>NOTE:</b> This is an automated email. Please do not reply.");

                    string CompIDs = string.Empty;
                    switch (Session["ISPCOMPID"].ToString())
                    {
                        case "1":
                            CompIDs = "1";
                            break;
                        case "2":
                            CompIDs = "2";
                            break;
                        case "3":
                            CompIDs = "3";
                            break;
                    }

                    smtpMail.SendMail(FROM_MAIL, ArrowGlobalFunc.GetEmailAddressesWithMgrs(CompIDs, Session["uID"].ToString()), ISP_COMPLETE, emailBody.ToString(), ArrowStrings.strSMTPserver, ArrowStrings.strSMTPuser, ArrowStrings.strSMTPpwd);
                }
                else
                {
                    sFinalValidationErrMsg = "<br/><br/>There was an error saving the data. ";
                    bWeGood = false;
                }
            }
}

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