Thumbnail select event

Hi,

help me.

when i run the script every functionality will be loaded and before loaded if i not select a thumb on bridge i got message which i given but  after loaded the script when i select a thumb get no message which pinrt.

function addFilelogScriptPalette(doc)

    {

             var sel = doc.selections;

             //$.writeln(sel.length);

             if(sel.length == 0)

             {

                 alert("Select file");

                 return false;

             }

            var fileName = sel[0].name;

          $.writeln(sel[0].name);

  }

i mean when i select every thumb i want to get each file inforation.

would u please help me in this regards.

Thanks.