In Excel 2003 also you can only set the outside boders using conditional
formatting, not the interior. However, you can use conditional formatting to
fill the cell with a pattern of diagonal lines from upper left to lower
right. To try it:

Select columns B & C.
Select Conditional Formatting from the Format menu.
Set the dropdown to "Formula Is".
In the formula box enter   =($A1="N/A")
Click the Format button.
Select the Patterns tab, then click the Pattern dropdown.
Choose a pattern, then click OK until the conditional formatting dialog is
closed.

Hope this helps,

Hutch