The edit button is only enabled for some types of data source - for example,
if your data source is an Excel file, it probably won't be enabled, probably
partly because Word cannot assume that it can update the data in an Excel
file without causing damage. In that case, you really have to open the Excel
file in Excel to modify the data. To do that, you may find that you also
either have to close the Mail Merge Main Document in Word, or disconnect the
data source (e.g. by setting the Mail Merge Main Document type to "Normal
Word Wocument). Closing is probably simpler for most users.
If your data source is an "Office Address List" (OAL) created from within
Word, then it /should/ be possible to edit it. However, these OAL files can
be damaged and in that case
a. I don't know any facilities in Word that will let you edit them
successfully
b. If you have Access, you may be able to open the file (it's a .mdb format
file) and edit it, but if you do Word will probably never be able to use it
as an OAL again
c. your best bet may be to try to export the data into another format.
