How to set the target folder for part within a customized auto association in Windchill PDMLink

How to set the target folder for part within a customized auto association?

I read support article CS277056, there they talk about the EPMWorkspaceHelper.manager.setTargetFolder API.

But when I tried to use it, it needs the new WTPart to be persistence, but on check in an error occurres with the message "The part is persistent!".

When the WTPart is not persistent the setTargetFolder function gets a null instead of a object id and doesn't execute. I get the following error: Cannot set target folder for objects that are not newly created.  1 out of 1 objects are not new.

Does someone have experience with it, and knows a solution?

Because I want the new WTParts to be in the same context as the EPMDocument when changing folder for new EPMDocument but not in the same folder, so the preference 'Store New Parts with CAD Documents' is not a solution.