I'm working for a client that has no version control system in place. I want to record changes to code without having to add all changes to a spreadsheet. I'm restricted to using Notepad++ so would a plugin or macro for this be another option?
Version control systems are those systems that allows you to capture changes and create a history for files. That's their purpose and the main reason for which they were created.
Therefore if you would like to record changes you should use a version control system, any one out there will do. Nevertheless you should still make and informed decision, and pick the most appropriate one.
Story: At my current job, during my initial employment weeks, I've received a task of creating a notifications service to be integrated into one of the companies internal applications. It happened that at the exact time the Configuration Manager, that was supposed to give me access to the company's source repository went on holiday. I've simply installed a VCS (Mercurial) locally and continued my work. When the CM came back from holidays, I've committed all my work into the company's repository.
Morale: even if there is no VCS available you can always use one locally.