Setting a subform instance with a subform

I have a subform within a subform, the first subform set the instance of the second subform using this script:

_ArthSngrs1.setInstances(this.rawValue);

When I save and reopen the document the data in the second subform from the other instances of the first subform all appear under the first instance of the first subform.

Any assistance would be greatly appreciated.

Best regards,

Parre