TrialSet |
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A.D. Tejpal
Microsoft MVP Joined: 30 Jun 2008 Status: Offline Points: 192 |
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Posted: 06 Jul 2008 at 10:27pm |
TrialSet
Updated On: 01-Jun-2012 Sample Db - Explanatory Notes General This sample demonstrates the process of preparing a front end db for trial use, by laying down the following settings -
(a) Number of permitted uses.
(b) Trial expiry date.
Out of (a) & (b) above, whichever falls earlier, displays a suitable message and causes the db to become unavailable for further use. Count of uses is stored in a hidden table named T_Status. Even if the user gains access to this table, and tries to edit it, the overall settings are not easily disturbed as the criteria is linked to autonumber value which is controlled programmatically. Expiry date, start number and max permitted uses get embedded in VBA code - and therefore free from user interference, once the file is converted to mde. Some interesting features for making the demo tamper-proof: 3 - Additional safeguards: 3.2 - The above super-string is stored in four separate ways as follows: 3.3 - On first run of trial db (signified by autonumber of table T_Staus being equal to hard coded value of starting autonumber coupled with the absence of database property, project property, registry key and special system hidden file), items 3.2 (a) to (d) above get created, duly populated with the superstring. 3.4 - On each closing of form F_SwitchBoard, existing value of autonumber in table T_Status is incremented by one and along with current date, is embedded in freshly generated 55 digit superstring. 3.5 - On each opening of form F_SwitchBoard, validity check is performed, covering: Usage: Before distributing an application with such features, following steps should be taken - 1 - In your db, open VBA window and set reference to Microsoft Scripting RunTime. For versions up to Access 2003, set reference to DAO 3.6 as well. (This reference is not required for Access 2007 onwards as it is already built in). Come back to database window. 2 - Import all objects from sample db into your db. These items are: 6 - Make sure that no form other than F_Switchboard is permitted to open independently. All forms should open only through F_SwithBoard and should also incorporate validity check for trial permissions. This is done by including suitable code in form's open event as demonstrated in sample form F_Next. 7 - Set F_SwitchBoard as the start up form. 8 - Go to VBA editor (press Alt + F11), save & compile (Debug > Compile). 9 - Come out of VBA window and convert to mde (or accde) format as applicable. Conversion to mde or accde format will succeed only if the following conditions are satisfied: Note: Version: Access 2000 File Format References: Download File >>: uploads/37/TrialSet.zip
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