Are you only going to make a ml? If you want to make, say 10 mls, scale it up. That way your measurements aren't so small.
If you were going to use 11 ml of your 24 mg/ml juice you'd add 1.5 ml of your 100 mg/ml nic base.
24 mg/ml * 11 ml = 264 mg nicotine
100 mg/ml * 2.0 ml = 200 mg nicotine
Total volume would be 13 ml. Total nicotine would be 464 mg. So, 464mg/13 ml = ~36 mg/ml.
Otherwise, you can somehow measure how many drops are in a ml of your nic base. Divide to get drops per ml, and figure it out that way. I prefer not to measure anything in drops, and I use syringes to measure small amounts of liquid.
Another option is to find a small 0.5 ml syringe (like for insulin). That would allow you to measure less than ml volumes more accurately.