private void tsbBilling_Click(object sender, EventArgs e)
 {
     if (!checkForActiveDoctors())
     {
         return;
     }
     InvoiceForm frmInvoice = new InvoiceForm();
     frmInvoice.MdiParent = this;
     frmInvoice.Show();
 }
 private void tsbBill_Click(object sender, EventArgs e)
 {
     InvoiceForm invForm = new InvoiceForm(m_patient.patID, true);
     invForm.MdiParent = MainParent.MainMDIParent;
     invForm.Show();
 }
 private void viewInvoice()
 {
     InvoiceForm frmInvoice = new InvoiceForm(m_selectedID);
     frmInvoice.MdiParent = MdiParent;
     frmInvoice.Show();
 }