OxyPlot LineSeries Tracker Property DataPoint

After the IDataPoint Interface was removed, I face the following problem:

I have a List of DataPoints, rendered as a LineSeries. I was working on converting these datapoints to a custom format to add my own property that should be calculated just-in-time (if possible) or beforehand if not.
As the IDataPoint Interface is missing I can not have a function on my CustomDataPoint to calculate the difference to a certain value as I intended to build:

(With TrackerString = "....{difference}")

MyDataPoint : IDataPoint
{
public string difference
{
get
{
return (certainDataValue-X)
...

As DataPoint is a struct I can not expand it to add this calculation. Do you know of any way that I can achieve this without implementing my own tracker feature?

Thanks alot!

0x54726F6E