Search Custom Record ID

Is it not possible to search a custom record be specifying the ID entered when the custom record was created e.g. 'customrecord_person' rather than the internal ID. We are going to deploy these custom records to another account where the internal ID is sure to be different.

The following code works:

             CustomRecordSearchBasic customRecordSearchBasic = new CustomRecordSearchBasic();              RecordRef cusRecRef = new RecordRef();              cusRecRef.setInternalId("114");              cusRecRef.setType(RecordType.customRecord);              customRecordSearchBasic.setRecType(cusRecRef); 

I have tried  cusRecRef.setExternalId("customrecord_person");

and cusRecRef.setName("customrecord_person");

but I just get an "Invalid custom record type" error.

Thanks,
Wayne Wundram
www.miraculum.com