CKfinder thumbnail

Hi
I'm using CKfinder and I'm trying to get the file thumbnail url rather than the fileurl does anyone know how exactly to pull this through.

function BrowseServer()
{
   // You can use the "CKFinder" class to render CKFinder in a page:
   var finder = new CKFinder();
   finder.basePath = '../';   // The path for the installation of CKFinder (default = "/ckfinder/").
   finder.selectActionFunction = SetFileField;
   finder.popup();
   //StartupPath = 'Images:/images/';
   
   // It can also be done in a single line, calling the "static"
   // popup( basePath, width, height, selectFunction ) function:
   // CKFinder.popup( '../', null, null, SetFileField ) ;
   //
   // The "popup" function can also accept an object as the only argument.
   // CKFinder.popup( { basePath : '../', selectActionFunction : SetFileField } ) ;
}

// This is a sample function which is called when a file is selected in CKFinder.
function SetFileField( fileUrl )
{
   document.getElementById( 'imagethumb' ).value = fileUrl;
   document.getElementById('imagedisplay').src = fileUrl;
}

I found this but I can't figure out how to implement it correctly

function ShowFileInfo( fileUrl, data )
{
   alert( 'The selected file URL is "' + fileUrl + '"' ) ;
 
   var formatDate = function( date ) {
      return date.substr(0,4) + "-" + date.substr(4,2)  + "-" + date.substr(6,2) + " " + date.substr(8,2) + ":" + date.substr(10,2) ;
   }
 
   alert( 'The selected file URL is: "' + data['fileUrl'] + '"' ) ;
   alert( 'The size of selected file is: "' + data['fileSize'] + 'KB"' ) ;
   alert( 'The selected file was last modifed on: "' + formatDate( data['fileDate'] ) + '"' ) ;
   alert( 'The data passed to the function is: "' + data['selectFunctionData'] + '"' ) ;
}

I tried this

function BrowseServer()
{
   // You can use the "CKFinder" class to render CKFinder in a page:
   var finder = new CKFinder();
   finder.basePath = '../';   // The path for the installation of CKFinder (default = "/ckfinder/").
   finder.selectActionFunction = SetFileField;
   
       //added line
       finder.SelectThumbnailFunction = ShowFileInfo;

   finder.popup();
   //StartupPath = 'Images:/images/';

}