How can we show confirmation message box from code behind and based on confirmation, perform further operation in ASP.NET VB ?

<pre lang="text">I have a button click event.
in it , 
after satisfying some condition, I should get a confirmation dialog.
When I click "OK" button of that confirmation dialog, I want to proceed further in my code on server side.

<pre>

<asp:ImageButton ID="btnCreateJob" ImageUrl="~/Images/btn_create_new_request.gif"
                            runat="server"  OnClick="btnCreateJob_Click" />

Setup.Aspx.vb Code
<pre lang="ASP.NET">Protected Sub btnCreateJob_Click(sender As Object, e As System.Web.UI.ImageClickEventArgs) Handles btnCreateJob.Click

        Dim UserID As String = ddlUsrId.SelectedValue.ToString()
        Dim requestType As String = ddlRequestTypes.SelectedValue.ToString()
        Dim producttype As String = ddlProduct.SelectedValue.ToString()
        Dim taxyear As String = ddlTaxyear.Items(0).Value
        Try
            If ddlRequestTypes.SelectedValue.Trim() = "RC1" AndAlso producttype = "M" AndAlso UserID = "UT" Then
                Dim Job_CreateTime As String = Common.Business.Jobsetup.GetCompletedCombinableJobsDetail(taxyear)
                If Job_CreateTime = "" Then
                    ScriptManager.RegisterStartupScript(Me.Page, Page.[GetType](), "showalert", "confirm('There is no request in the table. Please proceed with the request')", True)

                    'My doubt Is this
                    If (ok button clicked)
                        {
                          InsertNewJob(taxyear, UserID)
                        }
                        Else
                        {
                        //do Not insert
                        }
                     End If

                Else
                    ScriptManager.RegisterStartupScript(Me.Page, Page.[GetType](), "showalert", "confirm('The request is already submitted on " + Job_CreateTime + " do you want to place a new request?')", True)

                    If (ok button clicked)
                    {
                      InsertNewJob(taxyear, UserID)
                    }
                    Else
                    {
                    //do Not insert
                    }                   

                    End If
            End If
        Catch ex As Exception

        End Try
    End Sub

Protected Sub btnCreateJob_Click(sender As Object, e As System.Web.UI.ImageClickEventArgs) Handles btnCreateJob.Click

        Dim UserID As String = ddlUsrId.SelectedValue.ToString()
        Dim requestType As String = ddlRequestTypes.SelectedValue.ToString()
        Dim producttype As String = ddlProduct.SelectedValue.ToString()
        Dim taxyear As String = ddlTaxyear.Items(0).Value
        Try
            If ddlRequestTypes.SelectedValue.Trim() = "RC1" AndAlso producttype = "M" AndAlso UserID = "UT" Then
                Dim Job_CreateTime As String = Common.Business.Jobsetup.GetCompletedCombinableJobsDetail(taxyear)
                If Job_CreateTime = "" Then
                    ScriptManager.RegisterStartupScript(Me.Page, Page.[GetType](), "showalert", "confirm('There is no request in the table. Please proceed with the request')", True)

                    'My doubt Is this
                    If (ok button clicked)
                        {
                          InsertNewJob(taxyear, UserID)
                        }
                        Else
                        {
                        //do Not insert
                        }
                     End If

                Else
                    ScriptManager.RegisterStartupScript(Me.Page, Page.[GetType](), "showalert", "confirm('The request is already submitted on " + Job_CreateTime + " do you want to place a new request?')", True)

                    If (ok button clicked)
                    {
                      InsertNewJob(taxyear, UserID)
                    }
                    Else
                    {
                    //do Not insert
                    }                   

                    End If
            End If
        Catch ex As Exception

        End Try
    End Sub