Unfortunately not...Word is not really designed to do this stuff.

If you have Access you may be better off importing your data to Access and
using its reporting facilities.

Using fields, you can try starting with the example in the following KB
article:

http://support.microsoft.com/kb/211303

There are other ways to do it (e.g. using a DATABASE field to pick up
multiple lines per customer, but that does have some problems, or generating
your Word document from scratch using Word or Excel VBA) but I'd see how you
get on with the approach described in the article.

Sounds like you are trying to perform a "multiple items per condition (=key
field)" mailmerge which Word does not really have the ability to do:

See the "Group Multiple items for a single condition" item on fellow MVP
Cindy Meister's website at

http://homepage.swissonline.ch/cindymeister/mergfaq1.htm#DBPic

Or take a look at the following Knowledge Base Article

http://support.microsoft.com/default.aspx?scid=kb;en-us;211303

or at:

http://cornell.veplan.net/article.aspx?&a=3815