It sounds like you are trying to use the VLOOKUP function to reference cells that are outside of the worksheet size limit in Excel 2007. This can happen if you are trying to reference cells in a different worksheet or workbook that has more columns or rows than the one you are currently working in.

To fix this issue, you will need to adjust your VLOOKUP formula to only reference cells within the worksheet size limit. Here are some steps you can follow:

1. Check the cell references in your VLOOKUP formula to see if they are referencing cells outside of the worksheet size limit. You can do this by looking at the column and row numbers in the cell references.
2. If you find that your VLOOKUP formula is referencing cells outside of the worksheet size limit, you will need to adjust the formula to only reference cells within the limit. You can do this by changing the column and row numbers in the cell references.
3. If you are trying to reference cells in a different worksheet or workbook, you may need to copy and paste the data into your current worksheet to avoid referencing cells outside of the worksheet size limit.
4. Once you have adjusted your VLOOKUP formula to only reference cells within the worksheet size limit, you should be able to use the function without getting the error message.