As an alternative to installing the Analysis ToolPak, you could use
Erf(x) = GammaDist(x^2,0.5,1,TRUE)
ErfC(x) = ChiDist(2*x^2,1) = 2*NormSDist(-x*Sqrt(2))
ChiDist is more accurate than ErfC in all Excel versions. In Excel
2003, NormSDist is more accurate that either ErfC or ChiDist.

Jerry

Zhiming Qi wrote:

How can I download and install ERROR FUNCTION in Excel 2003? ERF() is not
available in my excel.
Thanks much!