Your project list doesn't need to have next actions in it. If you're storing next actions in Outlook it is redundant to have them listed again in Excel. By the way, you need to have at least one next action per project, but not only one so usually projects have many next actions, and this could be a limitation by using Excel.
If you want to organise your Outlook tasks by project, just use a project abbreviation or code at the beginning of the action name, eg Home reno: buy paint, so you can see at once all the projects and all the next actions in your Outlook list.
I originally started in Excel for my project list but moved to Word, so I have a file for each AOF, and each project is a heading in Word, and I have all the support info there, plus checklists for actions. So all the possible and future actions are in Word, and the next actions are in my list manager (Pocket Informant on the iPhone). I don't need these to link, and I don't write next actions in Word because that would be redundant and unnecessary.
Thank you for this advice. The project code is a good idea to link next actions while eliminating redundancy in the Projects and Next Actions lists. I think I'll give this a shot.