If they've provided a DLL then you can use the Call Library Function Node to call the DLL. You should read the chapter in the LabVIEW Help on calling code from external languages. If it's a C++ DLL you may have problems because LabVIEW only supports C DLL, not C++. A common issue is name mangling. If you do a search on the NI site for "DLL name mangling" you will come across several Knowledge Base articles that discuss this issue. Another common problem is that if the DLL uses complex datatypes (such as structures with strings inside, or pointers to complex structures then you will need to write a wrapper DLL that converts simple datatypes that LabVIEW can handle to the complex datatypes that the DLL uses. Again, there is a wealth of information on the NI site on calling DLLs, so a search will yield lots of information.
