Doing another merge is probably not what you need.

How are you inserting the "table name" and where are the table names?
Assuming each one is in a paragraph on its own, all you probably need to do
is to apply a heading paragraph style (say, Heading 1) to the paragraph in
the Mail merge main document. When you merge to a new document, each table
name will then be formatted as heading 1. You can then (manually) insert a
TOC field at the top of the document (e.g. { TOC \o "1-1" \h \z \u }),
select it, press F9 to update it, answer the question, and you should have a
ToC. If you have a look at Word Help for ToC fields you will see all the
options available to you.

(To insert the field, use ctrl-F9 to insert the {} and type the rest. But
when you have decided what field you need, you can create an Autotext from
it, which should make it easier to insert in the output.)

Peter Jamieson