If you're using Excel as a datasource, the only really congenial approach
that allows editing+merging without having to close your Excel file is to
use the old DDE method to connect to Excel. However, this has other
potential disadvantages (e.g. it favours connection to the first sheet in
your workbook and does not let Unicode characters through). But to do it, in
Word 2002/2003, check Tools|Options|general|"Confirm  conversion at open",
go through the process of connecting to your data again, and select the DDE
option in the additional prompt that appears.

Then ,what should happen is that when Word opens your mail merge main
document, it
a. sees if Excel is already open. If not, Word tries to open Excel
b. asks Excel via DDE whether the workbook you specified is open. if not,
Word asks Excel to open it
c. asks Excel for the data on the worksheet.

Because the sheet is open, you can edit the data. but in Word, you may need
to refresh Word's view of the data. In this case I can't tell you any more
what you have to do, but
d. Word may do it automatically from time to time
e. if not, if you open Word's Mail merge Recipients dialog box, you may be
able to click a Refresh button
f. if you added columns or made really significant changes to data types or
structures in Excel, you might have to re-connect to your data source to get
Word to see the changes.

Peter Jamieson