If you put this code in the ThisDocument module of your template it will
execute when a user tries to create a document based on the template:

Private Sub Document_New()

 On Error GoTo errorhandler:

 ActiveDocument.Save

 errorhandler:

   Select Case Err.Number
     Case 4198 'command failed
       MsgBox "You must save before continuing.", _
       vbExclamation, _
       "Save required"
       ActiveDocument.Close wdDoNotSaveChanges
     Case Else
       MsgBox Err.Number & " " & Err.Description
   End Select

End Sub