I have been using Borland C++ Builder 5 with NI-DAQ with no problems for about a year and a half. I am surprised by the "not supported" comment considering the fact that NI-DAQ comes with the Borland library files nidaq32b.lib and nidex32b.lib, which work fine. Include these, not the Microsoft C++ library files nidaq32.lib and nidex32.lib.
When the library files are not available, then you can use the implib.exe program in Borland C++ Builder's bin directory. For example, you would call it like this at the command prompt: implib nidaq32.dll nidaq32b.lib (naturally, nidaq32.dll must be in the current working directory for this example to work).