Are the extern correctly declared with = .... not only the function name? (function name only works only when you import codefiles but not if you import libraries)
did you import the file
is the DLL in the same directory as the exe (although this would not give an error at link time but when you run it)
did you import the file
is the DLL in the same directory as the exe (although this would not give an error at link time but when you run it)