I run another site called "Trust Funds for Kids" where I describe the basics of setting up a trust fund for someone else and also select stocks and monitor performance of those stocks via a pretty intricate (manual) system. Every six months or so I go through the effort of tracking every transaction and updating each portfolio in detail and I post the results out on the web through that site.
Every year for tax purposes I need to determine annual performance. In general, the funds don't have to pay much if anything in taxes unless there are capital gains from sales of stock (not offset by losses from sales of other shares). While taxes on kids' portfolios (in their name) can be complex, at a high level you don't need to file unless you have > $950 in dividends, interest and capital gains or unless you have to file anyways because the beneficiary has a job or other significant sources of income coming in.
There are five of these trust funds now and ultimately there will be eight, maybe more. I am sure that at some point I'll figure out how to use a tool but for now I just track them in excel. There actually a lot of effort in determining such simple concepts as "total return by stock" (dividends received plus unrealized gains and losses since the time you bought it) and also tracking the subsequent performance of stocks since you've sold them (the kids ask me about it, so I just suck it up and put it out there, I'm sure no other broker would do that). It also tracks the IRR of the portfolio, which also is much harder than it seems because you have different levels of investment coming in at various times so you can't just take what you've invested and look at current value (your "net" change) and divide by the number of years to get annual returns. I also track total fees since inception (buys and sells, plus any fees charged by the brokerage account) and it is good to see how these "direct" costs have declined over the 8 1/2 years since I started this effort.
If you are interested go over there and take a look. If you have a question throw a comment on something and I'll try to get to it. One thing that is kind of sad is the massive amount of comment spam I receive relative to the small number of postings and actual comments. It must be due to the fact that the site is financially related or something. Thank the heavens for Askimet, the anti-spam program I use for the wordpress blog.