Thanks, i had no programming experience ever before and could not really understand the meaning of residuals, and what is meaning of "t" you used? Sorry but is "a+b*t+c*t^n" equivalent to  "y=ax^n+bx+c" i was asking for?

Here is my two colums of data in excel, I have tried pasting them into the Vector braket, but the results i got was: a=0.000520, b=-865.64,c=865.64, n=1.000, this seems to far off from what i got from the "curving fitting assistant". thanks for your help once again.