A minor clarification: I think it might be possible to use separate script blocks, but for a period of time there was a bug that only one script block in each sheet was recognised. Ever since it's been a strong recommendation to use one script block. It's good practice for a separate reason: sometimes you have functions and constants that you want to use in multiple sheet workers. But each script block is completely isolated from each other, so you have to make copies of any shared data. Finally, when sheet editors work on a sheet, their javascript editing tools often work best if you have one large script block. So even if it's possible, there's no good reason to break up your sheet workers into separate script blocks. It's better to keep them all together.