John,
I respect your view point. If anyone else bumps onto this problem, here's how I am handling it.
PS: forcing to zero actually works quite well in my application: the first iteration starts at Skewness=0 (with a warning message) and then it wanders up and down as per the simulation, as desired.
Rgds
Gus
NEWCMD MYSKEWNESS Input Skewness @statistics ?"Computes the skewness of data in the input vector."
STDEV Input InputSD
IF InputSD = 0
DATA 0 Skewness
OUTPUT "WARNING: The standard deviation of your input data is nil. Skewness is not defined. Forcing result to zero to avoid crashing.\n"
ELSE
MEAN input inputMean
SIZE input inputSize
LET skewness = sum((input - inputMean)^3) / ((inputSize - 1)* (inputSD^3))
END
END