When you start Access for the first time after installing the Jet 4.0 SP8 update, and Access is set to either the Medium or High macro security level, you will see the message shown on the left.
What does this message mean? Simple — click Yes to block unsafe expressions and run Access in sandbox mode. Assuming that you are running Access at the High or Medium macro security level, you're all set — and you should not see any more messages about sandbox mode, unless you change the macro security level and then explicitly choose to allow blocked expressions.
If your macro security level is set to Low, you won't be prompted about blocking unsafe expressions when you start Access for the first time after installing the Jet update. Only when you change the macro security level to Medium or High will you see the message shown on the left. Change your macro security level to Medium or High, and then click Yes to block unsafe expressions.
You've probably noticed that this message does not actually mention "sandbox mode" at all, but it is important to understand that choosing to block unsafe expressions is sandbox mode. By clicking Yes, you are choosing to block unsafe expressions and therefore to run Access in sandbox mode. To turn off sandbox mode — which we strongly discourage — you would have to change the macro security level to Medium or High, and then click No when you are prompted whether you want to block unsafe expressions.
