Multi-Series Charts in Excel

I am increasingly fascinated with, and frustrated by, spreadsheets. Like most computer scientists, I have mostly ignored them, thinking that they were toys for non-programmers. The more I play with Excel for managing grading and other tasks, though, the more impressed I am.

But now I have a problem. I have three columns of data: the first is a date, the second is a project name, and the third is a count of lines of code. I want a time-series chart that shows the size of each project over time. The samples are irregularly spaced, and different projects are sampled at different times. Damned if I can figure out how to get Excel to do it. If anyone knows…