How to create own Blitz3D libs?

Can someone show and explain me an easy to understand and complete example, how to create own libs for Blitz3D?

All routines are not coded in Blitz and they are available as *.lib and *.dll files...

So how to create a headerfile or however this is called in Blitz3D (modul?) to link needed functions to the executeable and how to access the *.dll file? (also two ways are requested).

Btw. here is an test header in C... maybe someone can show me how to modify it and what i need, to get it work with Blitz3D... thanks.

#ifndef THISLIBNAME
#define THISLIBNAME
extern __declspec(dllimport) long __stdcall Test_Call1(TCHAR * sString1, TCHAR * sString2, long lValue1);
extern __declspec(dllimport) TCHAR * __stdcall Test_Call2(TCHAR * sString1, TCHAR * sString2, TCHAR * sString3, long lValue1, long lValue2);
extern __declspec(dllimport) TCHAR __stdcall Test_Call3(TCHAR * sString1);
extern __declspec(dllimport) float __stdcall Test_Call4(TCHAR * s);
extern __declspec(dllimport) double __stdcall Test_Call5(TCHAR * s);
#endif