User-suplied inputs:
Column B          Concentrations of the standards (X)
Column C	Instrument readings  of the standards (Y)
Column J	Instrument Readings of the unknowns

Calculated outputs:
Cell B28	n = number of x,y data points
Cell B27	sumx = ?x
Cell C27	sumy = ?y
Cell D27	sumxy = ?x*y
Cell E27	sumx2 = ?x*x
Cell F27	sumx3 = ?x^3
Cell G27	sumx3 = ?x^4
Cell H27	sumx2y = ?(x^2)*y
Cell B30	D = n*sumx2*sumx4+2*sumx*sumx2*sumx3-sumx2^3-sumx^2*sumx4-n*sumx3^2
Cell B31	a = (n*sumx2*sumx2y+sumx*sumx3*sumy+sumx*sumx2*sumxy-sumx2^2*sumy-sumx^2*sumx2y-n*sumx3*sumxy)/D
Cell B32	b = (n*sumx4*sumxy+sumx*sumx2*sumx2y+sumx2*sumx3*sumy-sumx2^2*sumxy-sumx*sumx4*sumy-n*sumx3*sumx2y)/D
Cell B33	c = (sumx2*sumx4*sumy+sumx2*sumx3*sumxy+sumx*sumx3*sumx2y-sumx2^2*sumx2y-sumx*sumx4*sumxy-sumx3^2*sumy)/D

Column K	Calculated concentration = (-b+SQRT(b*b-4*a*(c-InstrumentReading)))/(2*a)