I am trying to display a dialog box that pops up when you first open an excel
file. I want it to say...

Starting June 2005 we will be receiving a print out list of ATS (Application
Toolig Solutions) invoices that paid sales tax. This will be reported
quarterly.
This should be applied to the credit sheet

I want it to have an "ok" button to close the dialog box.

How do I do this?