Log username edited cell macro codes

I have excel file(excel 2003). I want to log the information that record username opening my file and the text is edited.


I search some codes in internet and i got this code...
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Sub LogInformation(LogMessage As String)
Const LogFileName As String = "C:\FOLDERNAME\TEXTFILE.LOG"
Dim FileNum As Integer
FileNum = FreeFile ' next file number
Open LogFileName For Append As #FileNum ' creates the file if it doesn't exist
Print #FileNum, LogMessage ' write information at the end of the text file
Close #FileNum ' close the file
End Sub
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Now, i have a problem when i execute this code. It does not work...
Anyone can comment this code?
I am just new in VBA codes....
Please help me...

Thank you
Akou

Anybody knows how to track changes in excel and log information like username in macro command?

Need your help....

Thank you.