Excel 2007 : protecting formulas in cells that data is entered

I need to be able to enter data across the row and have the word "Blank" in the rows below on the analytical Data tab. I have it setup that is column A ="" the the word "Blank" fills the cell. As soon as you enter "101" in A20 the word "Blank" starts to change to the data you are entering. You might use 1 row or 10 rows during 1 job. Then remove the sample numbers for the next job. I found even when I protect the sheet, when I remove the Sample numbers The word "Blank" does not show up. when I unprotect the sheet there are no more formulas in the line of cells that data was entered. I must show the "Blank" under the row that I am entering 1 sample in to show no more samples were taken.