Cannot rename a Cell in Microsoft Excel 2007

Hi,
I've been trying this for a couple of times. I created a document in Excel containing 5 values of my Market hour. I tried to rename each cell so I can refer the value of each cell later from my next sheet.
I just want to rename my first cell from OPEN to OPEN1, but it doesn't work. It always shows its first name which is OPEN not OPEN1 as I wanted.
I've tried this a couple of times just like I said. Is this a bug or some kind of error in my Microsoft Excel 2007 installation?
Anyone from Microsoft here? Thanks.


