below code can't catch the exception.

does catch can't catch the exception which occured in the function?

 try
            {
                Arche.Members.Feedback.FeedbackBiz_Tx a = new Arche.Members.Feedback.FeedbackBiz_Tx();
                a.AddFreeSubscriptionMember(itemNo, buyerID, itemName, DateTime.Today, DateTime.Today);
            }
            catch(Exception ex)
            {
                RegisterAlertScript(ex.Message);
            }

...

    public void AddFreeSubscriptionMember(string itemNo, string buyerID, string itemName, DateTime fsStartDate, DateTime fsEndDate)
    {
        FeedbackBiz_NTx bizNTx = new FeedbackBiz_NTx();

        if (bizNTx.ExistFreeSubscription(buyerID, itemNo))
        {
            throw new Exception("Exception.");
        }