Well.. the first task is to FIND their UserID file. Never hard code it because users can switch ID.
:First check "App Paths" to see if Notes is installed
$IsNotesInstalled=ReadValue('HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\notes.exe','Path')

The script then locates the notes.ini file from the following reg Key/Value:
HKCU\Software\Lotus\Notes\6.0
NotesIniPath
e.g. "C:\Documents and Settings\LLigetfa\Local Settings\Application Data\Lotus\Notes\Data\notes.ini"

That method only works on regular client installs. Administrator installs lack the \6.0 reg key.

The script then reads the INI file For the following Keys/Values:
[Notes]
Directory=
e.g. "C:\Documents and Settings\LLigetfa\Local Settings\Application Data\Lotus\Notes\Data"

KeyFilename=
e.g. "lligetfa.id"

$NotesIniPath=ReadValue('HKCU\Software\Lotus\Notes\6.0','NotesIniPath')
$Directory=ReadProfileString($NotesIniPath,'Notes','Directory')

You then need to determine if the ID file is in the current dir or another dir.
$KeyFilename=ReadProfileString($NotesIniPath,'Notes','KeyFilename')
If InStr($KeyFilename,'\')
$FileNames[0]=$KeyFilename
Else
$FileNames[0]=$Directory+'\'+$KeyFilename
EndIf

That's a start anyway.