Your particular use case is very interesting as we have been thinking a lot about it lately. There is no really easy way to do what you wish. Could you describe your application a bit more? Perhaps we can discover a better solution.
You mention that you won't know the functions that will be used in advance. Unfortunately, this will have some performance implications because any new script will need to be compiled before it can execute. If you did know the functions you were going to call, you could use some if or switch logic to implement a selector to choose among the different m-files.
It isn't possible to place the script into a MathScript node when the VI is running. Instead, what you'll want to do is bring up the file dialog for the user to choose a file. You can then use LabVIEW's Strip Path primitive to separate the path from the m-filename. You will also want to remove the .m extension from the filename so you just have the function name. You can pass the path and the function name into a MathScript Node that has all the other inputs and outputs configured per the common prototype. Simply call the 'path' function in MathScript to set the value you passed in to be the current path. Then, build a string by concatenating the output variables with the function name and the input parameters, e.g.
str = ['a = ' func_name '(x, y, z)']
With the path set, MathScript will be able to locate the function you are calling. To execute the function, use the 'eval' command. The 'eval' command also takes a slight performance hit in order to evaluate the string. If you also wanted to require that all functions have the same name (so that they are only differentiated by their location on the filesystem), you could improve performance slightly. By naming all the functions 'fname,' you could replace the string concatenation and eval call with a simple call to the function, .e.g.
a = fname(x, y, z)
and MathScript would use the function found in the current path.
Please let me know if you have further questions.
Grant M.
Staff Software Engineer | LabVIEW Math & Signal Processing | National Instruments
