Plotting alignments from heights and offsets

This is my first post, hopefully someone can help?

I want to be able to plot a platform adjacent to a designed centreline in Railtrack.

I have a spreadsheet of heights and offsets and chainages that takes into account end/centre throw and cant effects of the design.

I need to apply these offsets 'normal' to the alignment in order to generate co-ordinates along the platform edge at 2m intervals.

I'm not sure how to so this and my main concern is how the offset is calculated through a transition.  I assume it can't be done graphically as the displayed transitions are made up of a series of straights.  I need the co-ordinates to be accurate to within a millimetre due to extremely tight construction tolerances.

Any help gratefully recieved.