Importing empircal data and fitting a function to it

Hi

Any tips for the following: I have a data file filled with data concerning the viscosity of air at various temperatures. My goal is then to import the data, and fit a function to it, so that I have a continuous function eg. "viscosity(T)" that allows me to get an approximation for the viscosity of air for an arbitrary temperature.

have a nice weekend! and thanks for any suggestions :-)