Hi mahan8
For every sheet in the workbook do this
Click on the space above the first row header and on the left of the first column header.
All cells on the sheet are selected now
Ctrl 1 to open the format cells dialog
on the protection tab uncheck locked
After you do this select the cell you want to lock
Ctrl 1 to open the format cells dialog
on the protection tab check locked
Now protect every worksheet