I have tried the following but it fails   MessageDlg('Choose', mtConfirmation, [mbOK, mbYes, mbNo, mbCancel], MyCallback);   UniSession.AddJS('Ext.select("#ext-messagebox .x-button .x-text-el").elements[0].innerHTML="A"');   UniSession.AddJS('Ext.select("#ext-messagebox .x-button .x-text-el").elements[1].innerHTML="B"');   UniSession.AddJS('Ext.select("#ext-messagebox .x-button .x-text-el").elements[2].innerHTML="C"');   UniSession.AddJS('Ext.select("#ext-messagebox .x-button .x-tex