Thanks @2bfree for your input. I am aware that exchange fees still need to be accounted for. However, right now I am trying to find the relative percentage change of my last balance, accounting for all the previous transactions. I don't know what formula exactly I should be using for this.

OK, so I want to make a little profit calculator for myself based on my trade history from Poloniex.
Here's a purely fictional and simplified example:


In this example, I still have 5 ETC, which at the current rate is worth 0.011 BTC

But here's what I'm struggling with:

What is the percentage change of my current balance (5 ETC), relative to my previous transactions ?

Remember, I bought and sold at different rates!
I would like the percentage change to reflect a positive number, because overall, I still gained a profit of the ETC that I kept, even though I also sold most of it with a profit already.

Could someone please explain the steps on how I can calculate this? It would help a lot!