In Excel 2003, go to Tools -> Options.

Click on the General Tab.

Under the settings, Check or uncheck R1C1 reference style to use it or to change it to A1 reference style.

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In Excel 2007, Click the Office button and click Excel Options which you will find at the end near Exit Excel.

Go to Formulas tab and under Working with formulas, Check or uncheck R1C1 reference style to use it or to change it to A1 reference style.

Cheers,