Hi,

If you want to check something at the time of database write you can inherit write method :-

def write(self, cr, uid, ids, vals, context=None):
# --> your checking  code here
        return super(class, self).write(cr, uid, ids, vals, context=context)

write method get invoked every time we edit and save.

Or if you want to set a limitation or restriction for a field you can use _constraints or _sql_constraints:-

Using _constraints you can define Python constraints: here is syntax and example:-

_constraints
list of (constraint_function, message, fields)

def _check_company_id(self, cr, uid, ids, context=None):
        for statement in self.browse(cr, uid, ids, context=context):
            if statement.company_id.id != statement.period_id.company_id.id:
                return False        return True
    _constraints = [        (_check_company_id, 'The journal and period chosen have to belong to the same company.', ['journal_id','period_id']),    ]

using _sql_constraints, you can define SQL constraints to execute when generating the backing table. here is syntax and example

_sql_constraints
list of (name, sql_definition, message)

_sql_constraints = [ 
 ('number_uniq', 'unique(number, company_id, journal_id, type)', 
 'Invoice Number must be unique per Company!'),   
                    ]

Hope this helps.

Can you explain more detail what do you want to achieved (you problem) ?

i think you can do it  without JS