|Autocorrect is all or nothing. However, you can remove auto correction words from the office dictionary. To do that for excel 2007 and newer, click the windows icon/file button in the top left corner and click on options. Once in the options menu, click on 'Proofing' and click on the 'AutoCorrect Options' button.|
In the window that pops up on the 'AutoCorrect' tab, scroll through the list until you find 'hda-had' and delete it from the list.
Your other option is to just turn off the 'Replace text as you type' feature by un-selecting its check box.
Law of Logical Argument: Anything is possible if you don't know what you're talking about.