How are your users connecting to and opening your VBA Excel 2007 .xlsm file ?
If they are opening the file directly over an office network or LAN , only one person may open the file at one time for reading AND writing. Once a user opens the file it becomes locked to other users allowing them to open it for 'read' purposes only.
When the first user is done with the file and closes it, the 'write' lock is released allowing once again another user to open it for writing.
If you'd like for multiple users to be able to write to the file simultaneously you might want to look at giving users access to the file through a web interface or even via Excel which connects to a central excel file (or better still to a proper database application) using ADO
I hope this answers your question,
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