Hi,
There is an example here that leads you through the steps to building dynamic tables: http://assure.ly/gk8Q7a.
If you are using the table object, then you do not need to wrap this in a subform. If you select the row in the hierarchy, you can go to the Object > Binding palette and set it to Repeatable.
The other issue is to make sure that the form is saved as a Dynamic XML Form in the save-as dialog.
Hope that helps,
Niall