Class Library - How to pop up custom modal pop up?

Hi,

In my web forms app. I would like to call a dll function. But in this dll function I would like to pop up a modal dialog (customized) according to a specific condition. How can I make a such dll and use it in my web forms app?

Here is my sample class library;

Imports System.Web.UI
Imports System.Web

Public Class Utility

    Public Sub ManageExpenseCulture(message As String)
        Dim page As Page = DirectCast(HttpContext.Current.Handler, Page)
        ScriptManager.RegisterStartupScript(page, page.[GetType](), "script", "alert('" + message + "')", True)
    End Sub


End Class

Here is how I want my custom pop up;

        
          src="http://code.jquery.com/jquery-1.9.1.js">
   src="http://code.jquery.com/ui/1.10.2/jquery-ui.js">
  
    
  
  
  
                
                        
                
        
        
        
         
                 class="pen1">
                         class="handle">