Accessing DLLs through VBA
To call a function in a third-party DLL, you need to use the Declare statement. For example:
Private Declare Function GetTempPath Lib "kernel32" _ Alias "GetTempPathA" (ByVal nBufferLength As Long, _ ByVal lpBuffer As String) As LongSee How to: Access DLLs in Excel on MSDN for more information.
To list the functions that are available, take a look at the Dependency Walker tool, which will list the exported functions from DLLs (and lots of other information).