Hi,
I checked into the code of our w2m X function and extract the code that is used to calculate the fluctuation percentage. 

You may need to define a function as I show below to obtain this value separately:
double fluc(vector& vxy, double dTolPerc)
{
	vector vdiff;
	double dFluctPerc;
	vxy.Difference(vdiff);
	double min, max;
	vdiff.GetMinMax(min, max);
	double dMean;
	vdiff.Sum(dMean);
	dMean = dMean/(1.0*vdiff.GetSize());
	dFluctPerc = round(fabs(max - dMean)/fabs(dMean)*100, 2);
	return dFluctPerc;
}
To use it, suppose col(A) is your Y values col, you can run:
flucpercent = fluc(col(A),5) // where 5 is the tolerance you input
Regards!
Sean 
OriginLab Tech.