...
This requires that the custom field is marked as "show in app". We assume that the custom field has id=321.
if this.tasktype !== 45 && this.parenttodo == 0
subtodos = this.subtodos
if isarray(subtodos)
for id in subtodos
todo = Microbizz.GetTodoByID(id)
todo.sv("custom321custom322", this.custom321)
todo.save()
...