If DLL is WIN32, not COM DLL, you try on with this...

*|--
Declare Long LoadLibrary in "kernel32" String lpLibFileName
Declare Long GetProcAddress in "kernel32" LONG hModule, String lpProcName
Declare Long FreeLibrary in "kernel32" Long hLibModule

a = LoadLibrary( "C:\MyDll.dll" )
if( a != NULL )
*|-- DLL Exist
b = GetProcAddress( a, "MyDllProcName" )
if( b == NULL )
*|-- Function don't exist in dll.
else
*|-- Function EXIST in dll.
endif
endif

FreeLibrary(a)

*|--

Good Luck.