Thanks Brad.
I have made the changes to my code and it works!
NonLinearFitModelFunction= "(1-e^(-a*x)) * (b*x+c)" NonLinearFitIndepVariable= "x"
NonLinearFitCoefCount= 3
NonLinearFitCoefName(1)= "a"
NonLinearFitCoefName(2)= "b"
NonLinearFitCoefName(3)= "c"
NonLinearFitInitCoef(1)= 0.1
NonLinearFitInitCoef(2)= 0.1
NonLinearFitInitCoef(3)= 0.1
Tim
