Randomising the selection of different series, while keeping items within each series sequential

[wakecarter]

This is the standard solution. The only refinement I would recommend is to use selected rows instead of different spreadsheets.

Wakefield's Daily Tips

Avoid multiple spreadsheets One way of counterbalancing blocks in an experiment is to have an outer loop which points to a spreadsheet which contains the names of different spreadsheets to use in an inner loop. The main issue with this is that if you have multiple spreadsheets with the same columns and you want to make a change, you have to make it to all of them. The other more minor issue is that you may have to specify the spreadsheets as additional resources in Experiment Settings / Online. …