LabVIEW 4 is pretty old. I do not know if it even has a call library node. You may want to look in the LabVIEW user manual for more assistance with the call library node. Once you have read about it there (or verified it exists) you can download a document from NI's site called using external code in LabVIEW. Although it will be for a version newer than 4, I imagine the information would still apply.