Click the Office button, and then click Excel Options.
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In the left pane, Click Trust Center. Then click Trust Center Settings.

In the left pane, click Trusted Publishers.
Select a publisher, and then use the View and Remove buttons to make the changes.

In the left pane, click Trusted Locations.
Select a location, and then use the Add new location, Remove, and Modify buttons to make the changes.

Select or clear the Allow trusted locations on my network.

Select or clear the Disable all Trusted Locations, only files signed by Trusted Publishers will be trusted.
