Thank you for using the site.
Unless I have misunderstood what you are asking for, I think it would be relatively easy to set up a spreadsheet to do this. The challenge would be in updating the sheet when you add or delete stocks from your portfolio, or when you add or remove cash from it. If you keep track of cash additions during the year, those could be removed from the year-end value of the portfolio, and a percentage of growth or loss could be calculated that would reflect the change in stock prices over the year.
Alternatively, you could track the gain/loss of each stock purchase based on your buying and selling price (for your closed positions), or your buying price and the current price (for your open positions). These changes could be averaged to give you an indication of the overall success of your strategy or strategies. The drawback with this method is that if you have positions that span across two or more different years, it would take some extra effort to annualize the performance.
Does it sound like I'm on the right track here, or have I missed something?