You mean a builtin Matlab function?
That may be possible, but since it is bound by copyright you can't actually use that knowledge for a lot of purposes. (contact a lawyer if you would like to use that code/knowledge)
Some internal functions are not implemented in the Maltab language, but use compiled C code (or other languages, I don't work for Mathworks, so I don't know what they use internally). In that case it would only be possible to see what the code is doing by decompiling, which is likely either difficult, or illegal, or both.