jQuery iframe form submit

Is there any way to submit an iframed form from jQuery? What I have is the following:

$('button#bookingButton').click(function(){
    $('<iframe id="externalSite" class="externalSite" src="/form/page" />').dialog({
        title:'Form', 
        autoOpen: true, 
        width: 800, 
        height: 600, 
        modal: false, 
        resizable: false,
        buttons:{
            'Close':function(){$(this).dialog("close");},
            'Add Booking':function(){$('form#bookingForm').submit();}
        }
    }).width(800 - 25);
});

This creates a jQuery ui dialog which has an iframe within it. This works fine and the regular submit button works fine however the jQuery button does not submit the form.