How can I disable a button in a jQuery modal dialog from a function or at modal dialog load?

How can I disable a button in a jQuery modal dialog from a function or at modal dialog load?

Hi,
I'm new to JQuery.I have a jQuery dialog. In this form, I have a "Save" button. I would like this "Save" button to be disabled while the modal dialog open.

The code i wrote to create this button is given below. However, I don't know how to enable and disable the dialog button from a function or at the time of loading the dialog. What should I do?
 <pre>$('#divAddExpense').dialog({
                modal: true,
                autoOpen: false,
                height: 'auto',
                width: 650,
                draggable: true,
                position: 'center',
                resizable: false,
                buttons: { "Close": function () { $(this).dialog('close'); },
                        "Save": function (evt) {
                //Save click code here
                },
                close: function () {                   
                    //some code                  
                }
            });</pre>

Plz help me out.