Prevent Users Manipulating Time Out on Excel

[sabbuck]

Hi All,

I have a form on excel which is being used on a trial basis. Once the trial is up a message box appears to inform the user their trial has expired. If the expiry date in the code is 31/08/17 it should expire as today's date is 15/09/17...which it does. But I've realized if I manually change the date on my computer to say 29/08/17 then the code doesn't recognize today's actual date, it will only recognize the date I have set my computer to. Is there a way to prevent this? I don't want users being able to access this form after their trial has expired. The code I'm currently using is:

'Dim Edate As DateEdate = Format("30/09/2017", "DD/MM/YYYY")
If Date > Edate Then
MsgBox ("CURMIS Investment Register template was valid up to " & Format(Edate, "dd-mmm-yyyy") & " and will close.") & vbNewLine & " " & vbNewLine & "Please Contact Michael O'Grady & Co. for further use of this tool."
ActiveWorkbook.Close savechanges:=False'

 

[pjmorris]

hi Sabbuck,

Apologies for not providing a better steer, but the steps I'd take would be to access a remote time server to retrieve the time - provided the computer is connected to the internet I would expect it to work. I found more detail here: http://www.myengineeringworld.net/2013/09/retrieve-time-from-internet-server-vba.html but haven't had a chance to check it.

The alternative is to recognise that people are basically lazy and won't think to change the computer clock until after the event. Thus you could use the normal NOW() function and then use xlVeryHidden to hide the sheet in a way that normal users can't unhide. The code for this would be something like:

worksheets("Trial Sheet").visible=xlVeryHidden

you can unhide the sheet either programmatically by setting the visible property to 'True' or via the sheet properties in the VBE.

Final thought - make sure your code is password protected.

Hope this helps.

Regards

Peter