Reproject a Point

In My application I have to reproject a point from Australian Geographic GDA to Ttranverse mercatore  MGA zone 55.

I have a point

double x
double y

in GDA

and I want it in MGA94 for creeting a location.

Any help

Thanks
 

This compile but does not work :-(

                ITerrain6 tr = sgworld.Terrain;
                ICoordinateSystem6 csProject = tr.CoordinateSystem;
                ICoordServices6 ICoordServices = sgworld.CoordServices;
                ICoordinateSystem6 csGDA = ICoordServices.CreateCoordinateSystem("");
                ICoordServices.GetDistance(1,1,5,5);
                csGDA.InitFromEPSG(4283);
                ICoord2D cc = ICoordServices.Reproject(csProject, csGDA, x, y);