All office products updates are installed through windows update and if you have chosen automatic install of updates then the office 2010 updates will be downloaded and installed automatically. But if you want manually check for updates from Excel 2010 then you can use the option available as part of Help menu.
Click the File menu then Help menu. Now navigate to Tools for Working with Office section and click the Check for Updates option.
This would first launch the windows update page in Microsoft.com then the windows update screen under Control Panel will be displayed.
Click the available updates would display the list of updates for Operating system, Office 2010 and other Software.
Now you can pick and choose the required excel updates from the displayed list.