private void addNewPurchaseToolStripMenuItem_Click(object sender, EventArgs e)
        {
            FORM_PURCHASE_BILL frm = new FORM_PURCHASE_BILL();

            frm.ShowDialog();
        }
        private void button_add_Click(object sender, EventArgs e)
        {
            FORM_PURCHASE_BILL frm = new FORM_PURCHASE_BILL();

            frm.ShowDialog();
        }