A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
OneDrive is where the workbook is saved.
Excel Online is where you open the workbook in the browser, as opposed to Excel Desktop.
The CELL function works in Excel Desktop but is not supported in Excel Online.
There is no worksheet function replacement for Excel Online. You could write an Office Script, which is based on JavaScript, but this is not a very mature technology yet, and I don't expect it to be widely used for a long time.
When the file opens in Excel Online, click the Open in Desktop App button in the ribbon.