How RTC handles multi select of workitems while linking to an existing workitem

Hi everybody,
I am trying to link multiple related change request at a same time to a workitem..
I create a workitem-> Goes in the links section-> then in the related change request option i choose my custom change request objects to link/create existing change request.
While Linking an existing change request when I select multiple change requests through custom delegated dialog, RTC is linking only the first selected change request.
But when instead of custom, I choose multiple existing workitems to be linked to this new workitems, RTC is adding all of them at once as bulk link operation.
I want to know how RTC handles multi select or multi linking of related change request for custom change requests.

Thanks in advance