octave 3.0.2 cann't find existed user def ined oct file

[joyce]

hi all,
   I'm using Octave-3.0.2_i686-pc-mingw32_gcc-4.3.0 under windows xp, but after 
the example file myfunc.c compiled by mkoctfile and I typed myfunc in octave prompt
window, it shows message below:
> myfunc
error: `myfunc' undefined near line 4 column 1
octave-3.0.2.exe:4:D:\Octave\3.0.2_gcc-4.3.0\test

code of myfunc.c is as below:
 #include "mex.h"

 void
 mexFunction (int nlhs, mxArray *plhs[], int nrhs,
         const mxArray *prhs[])
 {
   const char *nm;
   nm = mexFunctionName ();
   mexPrintf ("You called function: %s\n", nm);
   if (strcmp (nm, "myfunc") == 0)
     mexPrintf ("This is the principal function\n", nm);
   return;
 }

I changed mkoctfile command as "mkoctfile --mex myfunc.c" and produced myfunc.mex,
however, the problem is still there. 
Even I move myfunc.oct to folder "D:\Octave\3.0.2_gcc-4.3.0\libexec\octave\3.0.2!
 \oct\i686-pc-mingw32", it still can not recognize this oct file.
Anybody can help me, please? 
Many thanks.

                                joyce