I posted this years ago and didn't get a particularly useful response. So I'll try again with a bit more information..
I'm trying to use auto publish on save to a location that is relative to the working drawing file location: "../tranmittals/current issue"
The default options available to me are no use- the only relative path is a subfolder in the drawing folder which is no use to me, the location has to be as above.
Previously I asked if there was a registry entry or a sysvar I could maul, well it turns out there is:
.....\profiles\autoCAD\Dialogs\ACAutoPublishOpts Location
I can input my preferred location into this key and it seems to work, as when I return to the autopublish dialogue in autocad the path is correct, i.e. ../tranmittals/current issue
The problem now is when it comes to publish time, Autocad fails to parse the ../ portion of the string properly, or even at all.
Looking at the plot log, I get "plotted with errors" the error being "ERROR: Error saving DWF file; DWF file is open or uneditable."
and the rest of the details being:
G
The Auto Publish settings are stored in the AutoCAD profile in the AcAutoPublishOpts section of the Windows registry as you noted, correct.
But since what you want to do will vary by which drawing you have open at the time (dozens of physical locations somehow taged with a partial entry/locator), I suspect you need to really ask in one of the Customization Forums for help creating a startup or 'reactor' to handle the edits the entry on a per-file basis.
Good luck.