The first thing to do is to read the manual called "Using External Code in LabVIEW". You can get to it by going to the help menu and selecting Search th LabVIEW Bookshelf. There is a function on the Advanced palette called Call library Node. This is used for calling a DLL. Reading the manual is the easy part. The hard part (usually) is going to be getting all of the required information from the vendor of the DLL. That means an explanation of each function in the DLL and the calling parameters for them. Some programs also have an ActiveX interface so that may be an option as well.
