http://exchangeserverinfo.com/2007/05/03/how-to-run-autoschedule-for-exmerge-utility.aspx
How to run auto-schedule for exmerge 
utility
 Note : For running exmerge utility we have to create a bat file.
1.   Create a folder called as “Exmerge” without quotation under C 
root drive 
2.   Copy only exmerge.exe and exchmen.dll under the 
Exmerge Folder 
3.   Run Exmerge utility 
4.   Select the 1st 
option i.e. (Export the mailboxes into .PST) 
5.   Follow the normal 
instruction as like we do 
6.   Select the number users for whom we 
want to create a .pst  file 
7.   click on save setting and then 
cancel the wizard 
8.   Now on Exmerge Folder, we will able to see 
exmerge.exe, exchmem.dll, exmerge.ini and mailboxes.txt 
      (Note:
 Mailboxes.txt is nothing but they are distinguished name for the users 
whom we selected)
9.   Open Exmerge.ini :- Check Mergeaction set it to “0” and check 
FilecontaininglistofMailboxes is pointing to Mailboxes.txt 
 
How to create a bat file for exmerge process
1.   Open the notepad type “ C:\exmerge\exmerge –b –f exmerge.ini” 
without quotation mark 
2.   Click on File, Save as and under save as
 box type “exmergetest.bat” (Don’t forget to put the quotation mark 
because bat file is created with the help of quotation mark only.) 
3.   Save
 that bat file under  C:\Exmerge Folder. 
4.   Just for test purpose 
you can run it through command prompt 
5.   CMD => cd exmerge and 
press enter 
6.   c:\exmerge> type “exmerge –b –f exmerge.ini” 
without quotation. 
7.   If you wish you can skip 5th and 6th point 
and directly go to control panel, select “Task Scheduling” 
8.   Select
 the exmergetest.bat file and fix the time to run . It will run.