Question about conditional formatting of zeros in Excel

[LordBolton]

Hi, I have a somewhat strange question about conditional formatting in an Excel spreadsheet:

I have a series of cells with different values. Some of them are blank, though, and this seems to be the tricky part. I have a certain conditional formatting rule which applies to positive numbers (font colour and cell fill colour), another to negative numbers (again font colour and cell fill colour) and yet another one for zeros (only font colour). The reason for not having cell fill colour in the last case is because when I try to add it, it is also applied to the blank cells in the range. And I want the blank cells to remain with the default background. They are not affected by the font colour rule because there is no font in them. They do have a fill colour, though (the default one). How to overcome this obstacle and differentiate the cells with 0.00 from those which are simply blank? If it would be relevant, they are all configured as currency values. As of now, the positive ones are defined with >0, the negative ones: with <0 and those equal to zero, with =0.

I'm sorry for the rather unintelligible description of the case in point, but the details are somewhat confusing in and on themselves.

Thanks in advance for any responses!