This is a very complicated calculation, because it transforms Cartesian coordinates on a flat surface to Geographical coordinates on the surface of the Earth. All depending where you are on the Earth, there are different factors to take into the equation.
I think this is the wrong place to wish for this, and if you do find a way, you can probably sell it for a lot of money.
You should get on to AutoDesk, and get the geodetic calculator to do batch transformations.
In Civil 3D there's built in functionality that allows you to transform data from one coordinate system into another. But it looks as if Jozi only has vanilla AutoCAD
LeeMac,
I am using this routine to save me alot of hard work in reworking points files. One thing though: it exports to 2 decimal places. Can this be changed to 3?