[netcdf-java] adding new variable to existing netcdf file ...

Hi,
I try to and new variable to an existing netcdf file. I open the file using, 

ncfile = NetcdfFileWritable.openExisting(....)
method, but when i adding variable with "ncfile.addVariable(....)", it gives me "not in define mode" error. How can i solve the problem. Is there any other method? Any suggestions will be helpful. 

Best wishes,

--ufuk