I need a lightweight mobile application that lets my remote team enter records directly into an existing Excel (.xlsx) file. The same codebase must compile for both iOS and Android. Core requirements • Offline functionality – users must be able to keep working without coverage; queued records should sync automatically when a connection returns. • Data validation – every field will have rules (required, numeric range, dropdown lists). Invalid entries should prompt friendly, inline messages. • Auto-save – progress is stored after each field so nothing is lost if the app is closed unexpectedly. Workflow 1. I will provide a sample Excel sheet that shows the final column order. 2. You build a simple form-based interface that maps one-to-one to those columns. 3. On sync, the app appends new rows to the sheet stored on OneDrive, Google Drive, or any other cloud location we agree on. 4. Once I confirm uploads work reliably from both platforms—even in airplane-offline-online test cycles—the job is done. Technology is flexible: React Native, Flutter, or any cross-platform stack capable of reading/writing XLSX files smoothly and passing App Store / Play Store test builds is fine with me. Deliverables • Full, well-commented source code • Instructions to reproduce iOS TestFlight and Android internal builds • Signed builds for initial testing • Basic README that shows how to change the target Excel file path Acceptance is complete when I can collect data in the field, turn airplane mode on/off, and see the new rows appear in the master workbook without errors.