Disable a button in a jQuery modal dialog while loading

Question

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 or from a function.

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?

---

 $('#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   
  }
  });

---

Plz help me out.