def fields_view_get(self, cr, uid, view_id=None, view_type='form', context=None, toolbar=False,submenu=False):
        result=super(account_invoice, self).fields_view_get(cr, uid, view_id, view_type, context, toolbar, submenu)
        if(view_type=='form'):
            invoice=self.pool.get('account.invoice')
            active_id=context.get('active_id',False)
            current_state=invoice.browse(cr,uid,active_id).state
            if current_state=="paid":
                result['arch']='''<form string="Invoice" edit="false" ....................></form>'''
        return result