grid flickering with checkbox and edit method

My purpose is to translate interactively a checkbox action into a couple of values "0001" or "".

I placed this method on a table whose name is Notification.

// BP Deviation Documented
edit NoYesId  provenWarranty (boolean _set = false, NoYesId _provenWarranty = NoYes::No)
{
    NoYesId provenWarr;
    ;
    // set value
    if (_set)
    {
        if (_provenWarranty)
            this.Func_Status = '0001';
        else
            this.Func_Status = '';
        return _provenWarranty;
    }

    // read value
    if (this.Func_Status == '0001')
        return NoYes::Yes;
    else
        return NoYes::No;    
}

This method is used by a Checkbox in a Form with this Table as a Datasource. This method has been cached in the Notification datasource init() method.

Notification_ds.cacheAddMethod(tablemethodstr(Notification, provenWarranty));

My problem is that the Checkbox is constantly flickering, is there a way to avoid that ?