Define which rows to show in Enum from ref


I have an enum of Product Ids to input orders into an order detail table. The Enum comes from the ref row type in the table “order details”. I would like to limit the options in the enum list to only show product ids where that product has more than 0 in the [Total Available] column in the product table. I’m not sure where I should be putting the expression before working out what that exoression should be.



The list of options presented in a dropdown menu is typically controlled with a Valid if expression: