Uploading multiple files at a time from Windows directory to Application under test

My Application has a 'Browse' button which opens up a windows Browse dialog upon click

My requirement is to select a folder in desktop and then select all the files in the folder and then click on 'Open' button on windows dialog

I'm unable to automate it using Auto IT

Can anyone help me out with the source code for this functionality

if clicking generates a file op en window directly this can be done by a simple way by calling sendkeys  method  with e full path name odf the file

if clicking on generates another browser window you have to take teh help  of code like 

Set windows = wd.getWindowHandles();

       for (String window : windows) 
       {
        wd.switchTo().window(window);
        System.out.println("Current Title Is    : " + wd.getTitle());
        if (!wd.getTitle().contains(MainWindowTitle))
        {
                         
                         }