I want to show message box on button click event in VB.Net web application , my code is -  
Public Sub MessageBox(ByVal msg As String)
    Dim lbl As New Label
    lbl.Text = "<script language='javascript'>" & Environment.NewLine & _
    "window.alert('" + msg + "')</script>"
    Page.Controls.Add(lbl)
    'End Sub
<asp:Button ID="btnGenerateReport" CssClass="Button100x25" runat="server" Text="View Report" />
Protected Sub btnGenerateReport_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnGenerateReport.Click
MessageBox("test message")
getreportdata()  // this is a function through which i am getting data in my crystel report
End Sub
i want before uploading data my message box should display. But through this code i am not able to.
Please help me.