Usually the W-ELP Solution is used in conjunction with Microsoft Word for

This document looks at the second option and gives hints how to make things easier inserting the needed commands using the MS Word print field (German Druck).

Usually there are those processes of interest:

First have a look how to add print fields to the document:

Older Versions: Insert -> Field -> Search in the right list box for Print/Druck and mark it.
Newer Versions: Insert -> Fast text modules / Schnellbausteine -> Field -> Search and mark Print

The classic trigger word example: PRINT "!THIS IS A !INVOICE!"

[If an invoice is printed]

Search_Binary=!THIS IS A !INVOICE!

; erase the trigger text

Erase_Binary=ON

; and make 2 copies form different trays

ELP_Command=K2;C1:1I9;C1:1I1;

Direct execute an ELP_Command: PRINT "<<K2;C1:1I9;C1:1I1;>>"

Direct call (3x) and overlay (4x) forms: PRINT 27"&fs1000y3x1S"

The 1000 is the ID of your form, and 3x will print the form only once on the page, 4x will print it on actual and all following pages until a new 4x comes or the overlay is ended with 5X PRINT 27"&f5X"

If you want to split up mail merge documents, add on the last page of each single document: PRINT 27"&fs25997y3x1S" or shorter PRINT 27")s-997Z"

Both options enter an internal ELP sequence and tells ELP to split the job on the next form feed, either in the archive or direct in the work flow.
Example: Stapling/punching and splitting mail merge documents explains this in detail. Here is just what you need for the second file split.ini, as the trigger command is already in the stream by the print field.

[GLOBAL]

OutPort=\\#HOSTNAME#\PrinterShareNameOfOutPort
NoPrinting=ON
OutPortMode_CollectFonts=ON

Need to change the field:

Older Versions: Extras -> Options ....
Newer Versions: Click on the icon top left -> button Word-Options -> open enhanced (Erweitert) ....

In that menus check for Field options and set the check box.

You may certainly set rules for searching any variable content or even as explained here for the document name.