Thread Subject: Modifying HDF5 files

Is it possible to _modify_ a dataset in an HDF5 file using the hdf5write function, without reading in the whole dataset first?

It seems that the two options for 'WriteMode' allow you to:
1) 'overwrite' - Wipe out all the data in the file, and create new datasets.
2) 'append' - Add new datasets to the file, but not modify existing ones.

I've looked at the documentation for the lower-level functions, but it seems more complicated than I was hoping for.

Thanks,

Mike