You're right, the IF function on its own is limited to comparisons within a single worksheet. Here are some expanded methods for comparing data between workbooks or sheets:

1. Formulas with Lookups and Indirect References:

- VLOOKUP/INDEX MATCH with Indirect References: These formulas are workhorses for retrieving data from different locations. VLOOKUP allows you to search for a specific value in a leftmost column of another sheet (or workbook with indirect references) and return a corresponding value from a different column. INDEX MATCH offers more flexibility for finding specific data based on row and column criteria. By combining these functions with INDIRECT references, which can construct cell addresses as text strings, you can reach data in other sheets or workbooks.

2. Consolidate Feature for Combining Data:

- Consolidate: This powerful tool lets you merge data from multiple worksheets or even workbooks into a single location. It's ideal for setting up comparisons side-by-side. You can specify the range of data to consolidate, arrange it in the desired order (rows or columns), and handle duplicates if needed. This creates a central comparison point for your data sets.

3. Spreadsheet Compare for Workbooks:

- Spreadsheet Compare (For Workbooks Only): If you're dealing specifically with entire workbooks that might have revisions or changes, Excel offers a built-in "Spreadsheet Compare" tool. This side-by-side comparison tool highlights differences between two versions of a workbook, pinpointing cell value changes, formatting variations, or formula modifications. It simplifies the process of identifying what has changed between workbook versions.

By understanding these techniques, you can effectively compare data across different parts of your spreadsheet or even between separate workbooks.