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-text-el").elements[3].innerHTML="D"');
Please advise - thanks