have users fill out coeff in C3:C6 and x variable in d4:d6, set d3 to
equal 1

Define coeff as your coeff array

set coeff= range ("C3:C6") ' Define coeff as your coeff array
set xi= range ("d3:d6") ' Define Xi as your variable x array

y =SUMPRODUCT(coeff,Xi)

this takes care of calculating y.....will play around with it to get
sum of squares

cheers,deano