Originally Posted by macropod

For the correct field coding to do this, check out my Microsoft Word Catalogue/Directory Mailmerge Tutorial in the 'Sticky' thread at the top of this forum:
Microsoft Word Catalogue/Directory Mailmerge Tutorial

The tutorial covers everything from list creation to the insertion & calculation of values in multi-record tables in letters. Do read the tutorial before trying to use the mailmerge document included with it.

The tutorial document includes working field codes for all of its examples, so most of the hard work has already been done for you - you should be able to do little more than copy/paste the relevant field codes into your own mailmerge main document, substitute/insert your own field names and adjust the formatting to get the results you desire. For some worked examples, see the attachments to the posts at:
mail merge with duplicate names but different dollar amounts
Access to Word, Creating a list from multiple records

Another option would be to use a DATABASE field in a normal ‘letter’ mailmerge main document and a macro to drive the process. An outline of this approach can be found at: Many to one email merge using tables - Microsoft Community
Conversely, if you're using a relational database or, Excel workbook with a separate table with just a single instance of each of the grouping criteria, a DATABASE field in a normal ‘letter’ mailmerge main document could be used without the need for a macro. An outline of this approach can be found at:
Mail Merge - To a Word Table on a Single Page - Microsoft Community
For some working examples, see:
Mail Merge: Using One Excel File with Multiple Sheets
Merge excel list into Word Receipt

Alternatively, you may want to try one of the Many-to-One Mail Merge add-ins, from:
Graham Mayor at https://www.gmayor.com/ManyToOne.htm ; or
Doug Robbins at https://onedrive.live.com/?cid=5AEDC...43615E886B!566