You'd have to use a font which displays 0s in such a way.

I don't know which font does that but I'm sure there is one out there. Just
experiment with different fonts.

Or perhaps google something like "calculator display font"

"jhe2006" wrote:

I have some codes that go to customers that contain both zeros and the letter
O. They look very similar and to avoid confusion, I have been requested to
make the zeros show up as zeros with a diagonal line across them.

I am using Excel 2003 SP2.