Iterate output path filename

[volition74]

Any of you guys got a method of iterating the output filename?

Rather than put a different setting in each json I create e.g
"output": "E:/Output Folder/output_01.mp4"

I was hoping I could iterate in say a batch file or PowerShell script

I tried the '--aerender-parameter' e.g.
--aerender-parameter 'E:/output_$i.mp4'
Where $i is an index and it just seems to hang there I don't get any errors but it doesn't process the render and I have to interrupt the script.

Any ideas would be appreciated.