HT> I entered the formula into a "spreadsheet"
 HT> but it gives me nonsense (negative values for the
 HT> relative humidity).  It's probably a typo, but I
 HT> can't find it.  Anyone want to kill some time
 HT> trying to find it?  Here's the cell entry:

 HT> 100*10^-(23.2801+(-5287.32/("Dry Bulb"+459.4)))*("Dry
 HT> Bulb"+459.4)^4.9283
 HT> *(10*(23.2801+(-5287.32/("Wet Bulb"+459.4)))
 HT> *("Wet
Bulb"+459.4)^-4.9283-(0.0003595+2.336e-007*"Wet Bulb")*
 HT> "Pressure"*("Dry Bulb"-"Wet Bulb"))

i put the above into excel just as you have it written but changing the
variables to cells (ie: "dry bulb" == A2) and then looking at the
formula in the pdf, i wrote it out on paper... then i matched up what i
wrote out with the formula in the spreadsheet... your problem is right
here...

 HT> 100*10^-(23.2801+(-5287.32/("Dry Bulb"+459.4)))*("Dry
 HT> Bulb"+459.4)^4.9283
 HT> *(10*(23.2801+(-5287.32/("Wet Bulb"+459.4)))
====-----^

that * should be a ^ ;) you were right, it was a typo ;)

taking the numbers from their Example 1 on page 19, i get pretty much the
proper answer they get...

theirs == p=29.7, T=75, T'=65.5, U=0.603 or 60.3 percent

  mine == p=29.7, T=75, T'=65.5, U=0.6025655547 or 60.25655547 percent

close enough for me and with rounding, it is 60.3 so i set that column of
cells to be in number format with one decimal place and let excel round it
for me ;)

 HT> *("Wet
Bulb"+459.4)^-4.9283-(0.0003595+2.336e-007*"Wet Bulb")*
 HT> "Pressure"*("Dry Bulb"-"Wet Bulb"))

HTH

)\/(ark