[jQuery] Questions about BlockUi

Hello,
is it possilbe to use a css when blocking an element? I just found a
way, to overwrite css parameters.
But it would be nice to use a css class. Perhaps like this:
$('#elementId').block({ class: 'cssClass' });
$('#elementId').unblock({ class: 'cssClass' });
Greetings,
Stefan Sturm