Re: Excel displays zeros as negative
Currency values are floating point values, and floating point values by definition aren't exact but only approximate.
Make judicious use of Excels round-function to change anything 'practically' 0.00 to 'exactly' 0.00.
Or use the 'precision as displayed' feature of Excel. See http://www.5starsupport.com/info/excel2k.htm, the last tip but one ("A quick way to round numbers"). But I don't know if this works in your case, because the conditional format doesn't do a calculation in the litteral sense.
Hope this helps.