Do you mean that you want a different jpeg for each record in Excel? If so,
let's suppose your Excel sheet hasa a column called picturefile with the
file name (say, mypicture.jpg) and that all the files are in a folde called
c:\mypictures. Then insert the following nested field in your Word mail
merge main document:

{ INCLUDEPICTURE "c:\\mypictures\\{ MERGEFIELD "picturefile" }" }

(You need to use e.g. ctrl-F9 to insert the special field braces {} )

You may need to check Tools|Options|Print|Update links and/or Update fields,
and if you are outputting to a new document you may need to select the
entire document (e.g. ctrl-A) and press F9 to update all the fields after
the merge.

Peter Jamieson