VB6 and Cabinet.dll. how it work

http://www.jsware.net/jsware/vbcode.php5#cab1

Creating and unpacking CAB files is often useful from VB, but VB is not capable of using the system file, cabinet.dll, that provides the functionality.

  Since VB cannot call the CDECL functions in cabinet.dll without a lot of acrobatics, the solution here is a very simple C++ DLL, made in VC6. It provides the basic functionality needed to extract from and create CAB files programmatically using cabinet.dll. This download includes a .CPP, .H and .DEF file. In combination with the LIB and header files from the Microsoft CAB SDK it provides everything needed to build your own DLL for use from VB.
   If you don't want to deal with C++ code, see the jsCAB download on the VBScripts page. It provides a pre-made ActiveX DLL for use with VBScript, as well as a compiled standard DLL for use from VB.

Download vbcab.zip (9 KB)

Here is some useful info from http://www.jsware.net/jsware/vbcode.php5

Creating and unpacking CAB files is often useful from VB, but VB is not capable of using the system file, cabinet.dll, that provides the functionality. So people are left to paste together hokey command-line alternatives, using makecab.exe, cabarc.exe, etc.

  If you look online for VB code you will find several examples that use SetupIterateCabinet, from setupapi.dll, for extracting from CAB files. One example is a project named Cab Explorer. There was also an in-depth article detailing the use of SetupIterateCabinet in the November, 2000 issue of VBPJ, by one Ken Getz. But SetupIterateCabinet doesn't really work! And none of the available code or articles bothers to mention that. SetupIterateCabinet can extract only from CAB files compressed using the MSZIP format. It fails if the CAB was compressed with the LZX or QUANTUM method. And LZX compression is actually fairly common.

   Other operations, like listing files in a CAB, can be done by directly parsing the CAB file header. So learning about the setupapi.dll functions is probably a waste of time.

   Since VB cannot call the CDECL functions in cabinet.dll without a lot of acrobatics, the solution here is a very simple C++ DLL, made in VC6. It provides the basic functionality needed to extract from and create CAB files programmatically using cabinet.dll. This download includes a .CPP, .H and .DEF file. In combination with the LIB and header files from the Microsoft CAB SDK it provides everything needed to build your own DLL for use from VB.
  If you don't want to deal with C++ code, see the jsCAB download on the VBScripts page. It provides a pre-made ActiveX DLL for use with VBScript, as well as a compiled standard DLL for use from VB.