Kee inside form when tabbing - how?

I have a form that opens inside an Ext.window.MessageBox.

The form has some fields, and a toolbar at the bottom with an 'Ok' and a 'Cancel'-button.

When the form opens, focus is placed in the first input-field.

If i press the TAB-key, it correctly advances to the next field. Keep pressing TAB and I reach the first button in the toolbar.

But then if I press TAB again,focus goes to the browsers address-field. I would very much like it to go back to the first input-field of the form. Is that possible?

-mads

Kee inside form when tabbing - how?