Conrad this scould help answer your curve fitting question <A HREF="http://www.qa-inc.com/knowledgecente/knowctrCurve_Fitting.htm" target="_new">http://www.qa-inc.com/knowledgecente/knowctrCurve_Fitting.htm</A> See number 5 <A HREF="http://philosophy.wisc.edu/forster/curve-fitting.htm" target="_new">http://philosophy.wisc.edu/forster/curve-fitting.htm</A> The more things change the more they stay the same. Irwin