[Aristarh Dark]

Вообще-то в справке есть, главное правильно искать:

HANDLE CreateFile(
LPCTSTR lpFileName, // pointer to name of the file
DWORD dwDesiredAccess, // access (read-write) mode
DWORD dwShareMode, // share mode
LPSECURITY_ATTRIBUTES lpSecurityAttributes, // pointer to security attributes
DWORD dwCreationDistribution, // how to create
DWORD dwFlagsAndAttributes, // file attributes
HANDLE hTemplateFile // handle to file with attributes to copy
);
...поскипано..
dwShareMode

Set of bit flags that specifies how the object can be shared. If dwShareMode is 0, the object cannot be shared. Subsequent open operations on the object will fail, until the handle is closed.
To share the object, use a combination of one or more of the following values:

Value Meaning
FILE_SHARE_DELETE Windows NT only: Subsequent open operations on the object will succeed only if delete access is requested.
FILE_SHARE_READ Subsequent open operations on the object will succeed only if read access is requested.
FILE_SHARE_WRITE Subsequent open operations on the object will succeed only if write access is requested.