I have a form "orders" and a subform "order details"

at "order details", depending on the selected "product type", some fileds should be shown.

the subform has all the fields possible for all the products types, wich are all hiden on load of the main form

i was thinking to show the necessary fields on user input of the product type field, but it seems like it isn't possible as it gives me the following error: "invalidTaskInSubForm"

Any ideas on doing this some other way?