What I think is going on here is: (though not exactly related to the topic header)
You have an attribute in RadScheduler, for which you
do not want the default text control, but
your own control, like a Combobox that could be populated with data as needed (parameterized data, based on other data)
So, first, do not create a resource, that comboboxes that is created by default, is way to difficult to manipulate on server side, rather use a attribute, which could be hidden (and populated with another controls events)
Lets assume you have a the following attibutes "Parent" and "Children". You know what "Parent"'s value is, before or during the FormCreated event, and you want "Children" to be a combobox with items retrieved each time from the database (dynamic), based on a value from "Parent".
And your Javascript function