Excel: Disable/Stop automatic capitalization
Display the Excel Options dialog box. (In Excel 2007 click the Office button and then click Excel Options. In Excel 2010 display the File tab of the ribbon and then click Options.)
Click Proofing at the left side of the dialog box.
Click AutoCorrect Options. Excel displays the AutoCorrect dialog box.
Make sure the AutoCorrect tab is displayed.
Clear the Capitalize First Letter of Sentences check box.
Click on OK.