There is a great KnowledgeBase article that discusses programmatically selecting printers from LabVIEW. This document can be found at:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/7bdcf84b1c2ce1f38025664f005568c8?OpenDocument
For reference, I found this document by going to www.ni.com, clicking on the KnowledgeBase link, and searching for "printer labview."