If you're asking how to determine the computer name of the client machine,
check out http://www.mvps.org/access/api/api0009.htm at "The Access Web"

Tools available from sites such as sysinternals.com can crack any
method you use to store a future date anywhere on a system such as in
the registry or a file.  Unless it's encrypted.  But even then if you
delete the date from wherever it's stored your app may think it's just
installed.

Thus I prefer to limit the number of records in one key table such as
5 units or 50 volunteers but allow unlimited access for everything
else.  Once I get paid then I email them an encrypted file containing
the number of records they are licensed for as well as their company
name which goes on the bottom of every page of every report.

For more of my thoughts on this topic see the "Copy protection or how
to safely distribute a demo Microsoft Access Application" page at
http://www.granite.ab.ca/access/demo.htm

Tony.