Excel Automation and Services

Excel exposes an Automation (COM) API that allows other applications to use Excel to create spreadsheets. This works fairly well if those other applications are interactive but some issues present themselves if they are services or command line utilities run by the Windows task scheduler. Those programs don't run in the context of an interactive user log in and Excel misbehaves if they try use it through Automation. Fortunately, it's possible to make this work by making a few configuration tweaks on the machine where the applications will run and by following a few rules when writing those applications.