How to reference subform data (pre-fill from existing data)

This sounds like it should be fairly straightforward - I have a form that has a subform which is filled out. A second form pre-fills in data from the information submitted.

I can't use this older information to fill in the subform in the new form. (other fields work perfectly fine)

I've tried:

z2=FormName [ID = IDofOld].SubformName;

And this returns the IDs of the subform.

If I just set the subform in the current form equal to the z2, I get an error when running the application saying:

Error Executing the workflow

Wrong DataType specified. The Template Variable Enter_Info should be of type NVIEW.

I can retrieve the data from the subform as a stringlist (z1 = (z2.Product_Name).getall()) and I also have another field that has the data in the subform as a comma separated value, but I haven't been able to update the subform using the stringlist.

I get errors like:

Error in executing Update Record task. Unable to update SubformName.Product_Name.

Unable to update the value Product Name Test....

Please help!

Thanks!