[Proj] converting from ITRF96 to UTM

[Marco Tuckner]

Hello,
I have coordinates which I would like to project from 
ITRF96 (EPSG:4917) to UTM.

The coordinates are present in x, y, z as cartesian coordinates in the geodetic
reference system ITRF96.
How do I transform them into UTM coordinates in geographic coordinates like UTM
(WGS 84 datum)?

If I'd just use proj4 and specify the EPSG number it tells me that the very EPSG
code is not supported.

There is a online converter at:
http://www.geodetic.gov.hk/smo/tform/tform.aspx
But it can only take geographic coordinates as input.

Any help is greatly appreciated.

Kind regards,
Marco