Short answer: No, you can't actually customize those headers.
But, maybe this will work for you:
Enter the headings you prefer to see in the cells of Row_1 and Col_A
Then, select B2
From the Excel main menu:
<window><freeze panes>
From the Excel main menu:
<tools><options><view tab>
UNcheck: Row & column headers
That will hide Excel's headers...leaving only your pseudo-headers visible.
Is that something you can work with?
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Regards,
Ron
XL2002, WinXP