The f(x,a) input for the Automatic mode of the polymorphic 'Non-Linear Curve Fit' VI requres a strict type def as an input.  If a user wants to control this function programmatically they must use VI Server property nodes in order to modify the various controls.

Use the attached example to programmatically control the value for f(x,a).  Note how VI Server property nodes are used to address various controls on the front panel of the template.  These controls can be linked to various parameters of the function, including constants, and can be changed without manually modifying the template.     Change control:

          John Smith 4/2/2007  This was a frustrating problem I spent a lot of time with, so I decided to share it with the community.