EXCEL: Why 65k Rows? How to Reset Vert Scroll?

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Esteemed Forum Participants and Lurkers:
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EXCEL

I have a workbook where I am trying to format the sheets with VBA so that they will print correctly. The idiots that edit the sheets have found innumerable ways to foul up my program. The latest one is nasty ... they have done something that makes the "UsedRange" function return 65533 rows. I don't know why it doesn't include the bottom 3 rows??? You can tell by the miniscule size of the vertical scroll button that a LOT of rows are active!

Anyway, I have looked at the cells and there doesn't seem to be any reason at all that the cells below the REAL actual used range should be considered active, but they definitely are. Is there any way to reset the Used Range? Does anyone have any idea as to what formatting (or other?) function drives the Used Range to the bottom of the sheet?

Any assistance in this inquiry is sincerely appreciated.