Assembly: Microsoft.Office.Interop.Excel (in microsoft.office.interop.excel.dll)
Use the AddIns property to return the AddIns collection.
Use the Add method to add an add-in to the list of available add-ins. The Add method adds an add-in to the list but doesn’t install the add-in. Set the Installed property of the add-in to True to install the add-in. To install an add-in that doesn’t appear in the list of available add-ins, you must first use the Add method and then set the Installed property. This can be done in a single step.
Use AddIns(index), where index is the add-in title or index number, to return a single AddIn object.
Don’t confuse the add-in title, which appears in the Add-Ins dialog box, with the add-in name, which is the file name of the add-in. You must spell the add-in title exactly as it’s spelled in the Add-Ins dialog box, but the capitalization doesn’t have to match.