A family of Microsoft word processing software products for creating web, email, and print documents.
First, you want to create a template rather than a document.
Use Content Controls.
See Word Content Controls by Greg Maxey and Create a Form Using Word Content Controls by Greg Maxey.
See also Repeating Data Using Document Property Content Controls and Other Mapped Content Controls
For setting up your letter template, see Setting Up Letter Templates - Ribbon by Suzanne Barnhill, MVP.
For the date, I would recommend instead of a place for someone to type, using a CreateDate field in your template.
If you want your documents to work in earlier non-ribbon versions of Word, you could consider using MacroButton Fields as Prompts.
(These need have nothing to do with macros.)