Scripting with Custom Child Record Sublists
Custom child record sublists are inline editor sublists. Consequently, they support all standard Scripting Subrecords that Occur on Sublist Lines. A custom child record sublist is unique only because it is not identified by a standard sublist internal ID, nor does it contain a standard set of field IDs. Otherwise, like all other inline editor sublists, you can add and remove line items. You can get and set values on existing line items, and the first line number (linenum) for all sublists is 1, not 0.
Important:
Be aware that you cannot perform validate line functions on custom child record sublists. Validate line functions are performed when a client event occurs prior to a line being added to a sublist.