How to install an Excel Add-in (XLA or XLL) with Automation

Summary

This article illustrates how to install an Excel Add-in (xla or xll) with Automation.

The following code demonstrates how to use Automation to:

Add a new workbook.
Call the Add method of the AddIns collection to add the new add-in to the list of add-ins in Excel Add-In Manager.
Set the Install property of the AddIn object to True (equivalent to selecting the add-in the Add-in Manager).
Dim oXL As Object, oAddin As Object Set oXL = CreateObject("Excel.Application") oXL.Workbooks.Add Set oAddin = oXL.AddIns.Add("C:\test.xla", True) oAddin.Installed = True oXL.Quit Set oXL = Nothing
Note that a workbook is added prior to calling the Add method in this example. The Add-in Manager in Excel is not available unless there is at least one visible workbook open. Without this line of code, you receive one of the following error messages:
Run-time error '1004':
Unable to get the Add property of the AddIns class
-or-
Run-time error '1004':
Add method of addins class failed.