This is a classic spreadsheet pain point, and the solution is hiding in plain sight. The user has built a smart workflow, querying a weekly roster onto a "Current event" tab, but hit a wall when they needed data to flow back in the opposite direction. They want to mark an attendance note on the front sheet and have it write back to the correct cell on the weekly roster. And they want to do it from a phone, without scripts. That's a fair constraint. The real issue isn't a missing feature; it's a missing design pattern.
The user is already comfortable with `QUERY`, which is a read-only function. It pulls data from elsewhere but cannot push data back. That's why the two options they considered feel awkward. Individual `QUERY` formulas per person on the weekly roster would work, but it's cumbersome to set up and maintain. A script is elegant but requires a desktop to edit and run. Neither fits their mobile-first workflow. The good news: there is a third path, and it doesn't require abandoning the spreadsheet paradigm.
The answer is a combination of `XLOOKUP` (or `INDEX`/`MATCH`, depending on the flavor of spreadsheet) and a carefully placed `IF` statement on the weekly roster sheet itself. Instead of trying to write from Sheet1 to Sheet2, the user can build a lookup on Sheet2 that reads the marker cell from Sheet1. For example, on the weekly roster, each person's row can include a formula like `=IF(Sheet1!B5="X", "Present", "")`. The marker cell on Sheet1 becomes the trigger; the weekly roster sheet reads it and updates itself. No scripts, no manual cell-by-cell queries, and fully functional on mobile. The user only needs to ensure the lookup references are consistent across weeks.
This approach respects the user's existing habits. They already manually update the `QUERY` each week to point to the new roster sheet. That same weekly update can include adjusting the lookup reference on the roster sheet. It's a small addition to a workflow they're already comfortable with. The key insight is that spreadsheet formulas can create bidirectional data flows if you design the architecture to read from the front sheet rather than write to the back sheet. The user isn't missing logic; they were thinking in terms of pushing data when pulling it is simpler and more mobile-friendly.