I have a spreadsheet in Excel that is basically a list of costs.

There are 12 columns and 200+ rows.

What I want to do is say something like "If the cell in column 12 is empty, hide the entire row"

I may also want to do "If the cell in column 3 is zero, hide the entire row"

How? I've worked out how to make text a different colour in a cell where, for example, a value s less than 20 but I dont know how to do anything more.

You can't do that in conditional formatting, it only affects how a cell looks, not whether it is shown at all. To make rows or columns hidden based on the contents of a cell is most likely something you will have to do in VBA (Visual Basic for Applications). I don't even think a macro will do the trick. The only 'kludge' to effectively not show the row would be to make the text white, but the row would still be there, you just couldn't see the data unless you looked in the status bar...

Would it be possible in access if I were to export from Excel ?

you should be able to do it in access - you just need to put a 'not null' into the criteria on column that you're interested in, in a query.... if you get what I mean?

Actually, in access I can simply sort the data and print a range that excludes the zero or empty fields.

yup, that's an option too I guess

You'll never really do this satisfactorily in Excel - since hiding columns or rows is just done by setting their width or height to zero. The data is still there and if you go and drag the separator to the right, or down, you can expose it again. Especially don't do this if you are planning on sending it to a customer.

Access - yes, very simple, as you say.

I don't know about whole columns or rows but, I 've always used :

=IF(A1=0,"",A1) where A1 is the cell that you want blank -- you can also use this to refer to other cell information or to enter "NIL" or something like that -- you would just put the text required inside the quotation marks.