Can't lock specific cells.

I unlocked the document and selected several cells but when I lock the document ... it's all or nothing.

I'd like to lock cells like the header and footer information.

help?

Forgot to mention - I tried several methods, including:

These steps:
1) Select the whole sheet (Ctrl+A), right click, Format Cells..., under Protection tab uncheck Lock option.

2) Select the range which you want to be locked (uneditable), right click, Format Cells..., under Protection tab check Lock option.


and these steps:

1) Select the whole sheet (Ctrl+A), right click, Format Cells..., under Protection tab uncheck Lock option.

2) Select the range which you want to be locked (uneditable), right click, Format Cells..., under Protection tab check Lock option.

3) Press F5, then Special button and check Formulas and hit Ok
--- I got an error message that no cells were selected.