by Allen Wyatt
(last updated August 24, 2019)
Shay works with a volunteer organization and they have developed an Excel workbook specifically for their volunteers. They don't want it copied or shared with outside individuals, so Shay wonders if there is a way to protect the workbook so that it will work only for a specific computer and no others.
There are ways to try to enforce security of workbooks, but there are considerations to take into account before settling on the best way. Understand that just about any approach is going to inconvenience users to one degree or another. Also, the approach you take may depend on whether the users are solely on your internal network or they are volunteers not connected to your network.
An easy way to start is to simply password-protect the workbook and then let your volunteers know the password. The two-fold drawback to this is that any password you pass on to your volunteers would continue to work after they were no longer volunteers and for anyone to whom the volunteers might pass the workbook. This is true even if you do an individual password for each volunteer.
Any other approach would rely on the addition of macros to the workbook. A great way is for the macro to check the name of the computer on which the workbook is being opened. This is an example of such a macro:
Private Sub Workbook_Open() Dim sComputerName As String Dim sPossible As String Dim sTemp As String sPossible = "[NEWDELL][Computer1][Order Entry][Dan's System]" sPossible = sPossible & "[Computer2][Computer3]" sComputerName = Environ("computername") sTemp = "[" & sComputerName & "]" If InStr(sPossible, sTemp) Then MsgBox "Welcome to the workbook." Else MsgBox "You are not authorized to open this workbook." Workbooks(ActiveWorkbook.Name).Close SaveChanges:=False End If End Sub
The idea behind the macro is that you would define, in the sPossible string, the names of each computer on which it is permissible to open the workbook. All you need to do is make sure you get the machine names spelled exactly correctly and enclose them within square brackets in the sPossible string. The Environ function returns the actual computer name, it is placed in the sTemp variable within the brackets, and then the InStr function is used to see if it is in the list of possible machines. If it is, then a message box is displayed; if it isn't, then a message box is displayed, and the workbook is closed without saving any changes.
If you prefer something even a bit more secure, you could also use the Environ function to return the "username" value, which would give you the username for the account being used on the computer.
This macro approach is relatively simple, but it does require knowing computer names (and/or usernames) before it will work properly. It also assumes that the user doesn't know enough about Excel to bypass macros by holding down the Shift key as the program starts. If you suspect the user may know that much, you'll need to take more steps, such as the following:
Using this approach makes sure that even if the user disables macros (by holding down the Shift key during startup), he or she cannot get to the worksheets because a macro is required to make them visible.
You could utilize a variation on the above approach so that instead of relying on the Environ function you could have the macro check for the presence of a predetermined file in a particular location on the system. This means, of course, that you need a way to get your hands on the system ahead of time to put the proper file in the proper location.
Finally, whatever macro-based approach you choose, you should ensure that the VBA project for the workbook is protected with a password. This will stop someone from going and looking at your macro code to figure out what is going on with the protection.
There is something else you always need to keep in mind when trying to secure your workbooks: Whatever safeguards you put in place can always be circumvented with enough knowledge and patience. If your users are not that technically sophisticated, then you should have no problems. If they know a lot about Excel and macros, however, then all bets are off.
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