How to re-display a report preview?

hsm

I have an invoice report.

A custom button on the preview (see picture) exports the invoice to a file and takes the user to a modal form where they can email it to the customer, adding a message if they like.

procedure TFrmInvoice.ButtonClick(Sender: TObject);  //send invoice by email
   Get customer email address from database
   Set up subject line and body
   Open modal form to send email
   Case modal result of
       mrOK: show message 1
       mrCancel: show message 2
       end // case
  end; //buttonEmail