I have created a performance report in Excel 2003 which references values from 4 other spreadsheets.

However, for some reason it now only recognises one spreadsheet. For example, when I type '=' into a cell and then open another xls, it won't allow me to continue with the formula.

Also, the full directory of the other xls file is displayed in the formula bar even though the other xls is open and sitting in the same folder.

Does anyone have any ideas?