You can run the same command in nested "for" loop with incrementing parameter that will be user name suffix.
That should work fairly well.
It will run really really slow if you do it in a for loop in a batch file, but it will work.
I would rewrite in VBS and use a persistent connection, it takes about 20x the effort to create a user as it does to login to the API, so by using a persistent connection you can run all the creation events in one big transaction. You could use any of the sample scripts I published, they all have a vbs wrapper for SBadmCL in them with the createuser command.