LoadLibrary

@ DLL
extern "C" __declspec(dllexport) double SquareRoot(double d);

@ caller

typedef double (SQRTPROC) (double);
SQRTPROC* pFunc;
HMODULE hMod = ::LoadLibrary(_T("xxx.dll"));

if(hMod)
{
    pFunc = (SQRTPROC*)::GetProcAddress(hMod, " SquareRoot ");
    if(pFunc)
       double d = (*pFunc)(1.0);
}