Dunty,
The syntax will probably be something like "ob0!sc1!md1!2:6".
Take a look at the following Knowledge Base article:
Valid SCXI Channel String Arrays under LabVIEW
http://digital.ni.com/public.nsf/websearch/6FC83B7AC9ACA5788625615B00823D65?OpenDocument
Regards,
Justin Britten
Applications Engineer
National Instruments