First, you may find it easier to produce what you want in Access using its
Report generator anyway. I'm not so familiar with that.

I'm still not clear what you want - if it's one /row/ per member in a table,
it's generally best to set your mail merge main document up as a single-row
table with one column for each field. Put one mergefield in each cell.
Don't have anything else in the mail merge main document - not even extra
paragraph marks. Merge to a new document, then add a row to the table for
headings.

However, a tabular layout like that may not be so good at dealing with
this...

How to do that depends partly on your table structure. if all the optional
information is in a single record in Access, I suspect what you need is
something along the general lines of

Name          Other details                Interests
<<Name>>  <<some field name>> <<Interest field A>>
                                                     <<Interest field B>>
                                                     <<Interest field C>>
etc. up to the 20th interest field.

where the fields and header are aligned using tabs (you probably won't see
it like that in this message). Word should remove lines where the interest
fields are blank.

If on the other hand you have a separate interest table, you may need
something else. But let's cross that bridge if we come to it.

If that's not the problem, have another go at spelling it out...

Peter Jamieson