Hi VZn-
I'm not sure exactly what you're trying to do, but here are some links to other discussion forums that include example VIs:
And here's a KnowledgeBase article with an example attached:
I also want to point out that LabVIEW no longer supports this VI in later versions, and National Instruments recommends using the Nonlinear Curve Fit.vi instead.
Hope this helps!
Drew Pierce | District Manager, Central Texas | National Instruments