This functionality is not supported out-of-the-box. Our GridControl, as well as any standard control, does not directly work with physical files. There are many reasons for this. For example, it is not possible to get notifications when some part of a physical file is changed. Thus, it will be necessary to reload the entire file each time the GridControl's content needs to be refreshed. Also, to save each change made in GridControl, it will be necessary to access this file again. Thus, dealing with physical files directly will be very slow.
That is why, to open an Excel file in GridControl, it is necessary to use an approach that you would use with a standard DataGridView control: populate a DataSet with data from an Excel file and then bind the grid control to this DataSet. To do this, you can use the Microsoft OLE DB Provider for Microsoft Jet. These solutions are described in the following articles:
Microsoft OLE DB Provider for Microsoft Jet
Import Excel File to DataSet - CodeProject
This example demonstrates this approach in action.