private void toolStripButton2_Click(object sender, EventArgs e)
        {
            Form13 childForm = new Form13();

            childForm.MdiParent = this;
            childForm.Show();
        }
        private void storeIncomeToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Form13 income = new Form13();

            income.ShowDialog();
        }