I imagine that as you have a comma delimited file, it may have come out of
some database application in which case, that is probably the best place to
do this.

It's not something that Word has any in-built capability to do, but you can
take a look at the "Multiple items per condition" item under the "Special
merges" section of fellow MVP CIndy Meister's website at
http://homepage.swissonline.ch/cindymeister/MergFram.htm

Or, if you create a catalog type mailmerge with a table in it in which you
have the name and address details in the first column with the transaction
date and details in other columns and you execute that merge and then run
the following macro over the resulting document, it will create a separate
table for each name and address with that information in the first row of
the table and the transaction details for that name in the following rows:

' Macro created by Doug Robbins to create multiple items per condition in
separate tables
' from a directory type mailmerge

Dim source As Document, target As Document, scat As Range, tcat As Range

Dim data As Range, stab As Table, ttab As Table

Dim i As Long, j As Long, k As Long, n As Long

Set source = ActiveDocument

Set target = Documents.Add

Set stab = source.Tables(1)

k = stab.Columns.Count

Set ttab = target.Tables.Add(Range:=Selection.Range, numrows:=1,
numcolumns:=k - 1)

Set scat = stab.Cell(1, 1).Range

scat.End = scat.End - 1

ttab.Cell(1, 1).Range = scat

j = ttab.Rows.Count

For i = 1 To stab.Rows.Count

   Set tcat = ttab.Cell(j, 1).Range

   tcat.End = tcat.End - 1

   Set scat = stab.Cell(i, 1).Range

   scat.End = scat.End - 1

   If scat <> tcat Then

       ttab.Rows.Add

       j = ttab.Rows.Count

       ttab.Cell(j, 1).Range = scat

       ttab.Cell(j, 1).Range.Paragraphs(1).PageBreakBefore = True

       ttab.Rows.Add

       ttab.Cell(j + 1, 1).Range.Paragraphs(1).PageBreakBefore = False

       For n = 2 To k

           Set data = stab.Cell(i, n).Range

           data.End = data.End - 1

           ttab.Cell(ttab.Rows.Count, n - 1).Range = data

       Next n

   Else

       ttab.Rows.Add

       For n = 2 To k

           Set data = stab.Cell(i, n).Range

           data.End = data.End - 1

           ttab.Cell(ttab.Rows.Count, n - 1).Range = data

       Next n

   End If

Next i