[timchristie]

There are a few interesting hacks you can do, the calls are slow to an individual cell (I think like 50-100ms). If you need arbitrary cells, you can use a sheet formula to put the desired result in a single cell.

For example I had a sheet that had hundreds of columns that the headers would change over time - instead of reading through each cell, I just used CONCATENATE(), read a single cell then split it in my program after pulling it.