How to calculate the errors for combinations of eff histograms

EffCombination.py

  asymErrorCumu = r.TGraphAsymmErrors()
  asymErrorCumu.Divide(cumuNomTotal,cumuDenomTotal)

  for bin in range(CumuNomList[0].GetNbinsX()):
    binLumi = 0
    BinEff = 0.
    point = bin + 1
    errPlus = 0.
    errMinus = 0.
    yval = 0.
    xvalAtPoint = r.Double(0)
    yvalAtPoint = r.Double(0)
    pointEff = r.Double(0)
    xOfPoint = r.Double(0)
    asymErrorCumu.GetPoint(point,xOfPoint,r.Double(0))
    for numerator,denominator,weight,TEff in zip(CumuNomList,CumuDenomList,values[1],collectionCumu):
      if int(denominator.GetBinContent(bin)) is not 0:
        binLumi += weight
        TEff.GetPoint(point,xvalAtPoint,pointEff)
        BinEff += (pointEff*weight)
        errPlus += (TEff.GetErrorYhigh(point)**2 * weight**2)
        errMinus += (TEff.GetErrorYlow(point)**2 * weight**2)
        # This is our efficiency for the bin.
    if int(binLumi) == 0: binLumi = 1.
    BinEff /= binLumi
    errPlus = math.sqrt(errPlus/ (binLumi**2))

    errMinus = math.sqrt(errMinus/ (binLumi**2))
    print "Point = %f,%f, + %f, -%f"%(xOfPoint,BinEff,errPlus,errMinus)
    # Now we need to set the errors and points of our histogram!!!
    # if int(xvalAtPoint) is not 0: