In python, I have the following field:

'permit':fields.selection([('new', 'New'),
            ('applied', 'Applied'),
            ('received','Received')], 'Permit', select=True), 

def apply_permit(self, cr, uid, ids, context=None):
        data = {'value': {'permit':'applied'}}
        return data

In XML, I have the following:

 <field name="permit" readonly="True"/>
 <button name="apply_permit" string="Apply" type="action" class="oe_highlight" attrs="{'invisible':[('permit','=','applied')]}" />

The attrs code above doesn't currently work but what I want to do is: when click on the button 'permit' field value will be set to 'applied' and then hide the button.All these done before the form save. The button is inside the form.