Shift in my Coordinate conversion

Anyone out there with a solution for me??? for the shift am getting in my coordinate conversion....
Yea, I try to convert WGS84 to GDA1994MGA_50 am getting the shift in my result.
I get the WGS84 coordinates @ runtime and I convert SR the below way which results in a shift :( :( .....

private static IGeometry5 ConversionFromWGS84(IGeometry5 geometryFromWGS)

        {

            ISpatialReferenceFactory SRFactory = null

            Type t = Type.GetTypeFromProgID("esriGeometry.SpatialReferenceEnvironment");

            object obj = Activator.CreateInstance(t);

            SRFactory = obj as ISpatialReferenceFactory;

            ISpatialReference srGCS = new GeographicCoordinateSystemClass();

            ISpatialReference srPCS = new ProjectedCoordinateSystemClass();

            srGCS = SRFactory.CreateGeographicCoordinateSystem((int)esriSRGeoCSType.esriSRGeoCS_WGS1984);

            srPCS = SRFactory.CreateProjectedCoordinateSystem(m_Document.FocusMap.SpatialReference.FactoryCode); 

            geometryFromWGS.SpatialReference = srGCS;

            geometryFromWGS.Project(srPCS);

            return geometryFromWGS;

        }

I even tried implementing IGeoTransformation but no luck

sometimes unhappy coding too .....

regards

Rajesh K