Close second workbook

I have a Workbook in Dropbox that can be shared with several users. In an attempt to stop a user from opening the workbook while it is opened by another user, I do the following.
[I am SORRY but I do not know where the Code Tag is. I know that I need to put my code within this tag but ...]

in ThisBorkBook Workbook_Open:

I look for a specific file "LOCK_FILE"

If "LOCK_FILE" does not exist, I ask the User for their name and then create "LOCK_FILE" with the current user's name as the first and only line in the text file.
The Excel app then goes about its business with the user running various options from the "Welcome/Menu Page".
When the user selects Exit from the "Welcome/Menu Page", I delete "LOCK_FILE" and Save and Quit the Excel app.

If "LOCK_FILE" does exist, I display a message indicating who is using the file from the info in "LOCK_FILE".
I then attempt to Close the Excel "instance" just opened. NOTE: This is the issue.
The second user can then try to "sign in" at some other time.
If the same user has the file for a long period, they can be notified and hopefully will close the Excel app.

To this point, I have not been successful in closing this second "instance" of the Excel app.
I have tried various things that work in Debug mode but will not do the job in "real time".
My last attempt brings up a blank workbook after the close.

I would add the code here but it is a mess because of so many attempts to solve my issue.
Also if someone could explain how to use the Code Tag, I will supply what code I have, mess or not.


I am sure there are other ways to accomplish what I am attempting to do.
I do like having the ability to know who has the file open so that the second user can contact them to see when they might be finished or if they just forgot to Exit the app.
I plan to have additional information in the lock file such as start time, user email address, user phone number, and other various pieces of information.

Final comment. I am testing using just one computer. In real life, the users will be on their computers.
I do have two computers and do not believe that this makes any difference in execution but I have not "wrestled it to the ground" yet.

Thanks for any help you might provide.

Dan

I believe that I have followed the instructions.

Hopefully, a text file containing my code for the "ThisWorkBook Open" routine is attached.

I went back and checked and I did not get it the first time. I believe it is there now!

Thanks for your help.

Dan

OK, I have attached the app as it stands right now.
It is a work in progress.

Thank you for staying with me on this.

Dan

I missed your question about the Sub xxx_Workbook_beforeClose(cancel as Boolean). This is an attempt to capture someone selecting the "X" to exit rather than using the supplied Menu Option. I don't know if the xxx's are to indicate that it is for an "X" exit or if I put them there so the subroutine would not execute. It seems as though I tested that yesterday and was taken here when I closed the app with the "X". (I had but a Stop statement in the code or did a break on the keyboard to get into the VBA code.

Thanks for letting me know what it is I am doing. I think I will remove the xxx and test it again.

The original problem, however, is attempting to close a second occurrence of an Excell workbook.

I have resolved my issue in a less-than-glamorous way. When I close, I have an empty Excel session. Before issuing the close command, I put out a message asking the use to close the window using the "X". This works every time but as I say it is not yet the "final answer". Any other thoughts?

Thank you for the reply. I did wonder about Quit rather than Close. I have uploaded the current version.
Dan