There is little you can do. This topic has already been discussed ad nauseum at the MathWorks web forums.
@noah has provided an example of numerical differentiation (ie: differencing) on a finite data set, whereas you are looking for a means of doing symbolic differentiation of continuous-domain-continuous-range function applied to a discrete-domain data set.
In short, not happening. You're asking how to install a shelf without a hammer, screw driver, or nails. You could always just download and install GNU Octave, a free alternative to MATLAB.
References.
- "Symbolic Math In MATLAB" http://faraday.elec.uow.edu.au/subjects/annual/ECTE313/Symbolic_Maths.pdf
- "Symbolic differentiation without symbolic math toolbox" http://www.mathworks.com/matlabcentral/newsreader/view_thread/83397
- "GNU Octave - Download" http://www.gnu.org/software/octave/
- "Symbolic differentiation with GNU Octave" http://octave.1599824.n4.nabble.com/Examples-for-use-of-symbolic-toolbox-td1601724.html