Making a few assumptions, I did a quick check.

F20 118d, May 2014, 60k miles, Manual, 5dr, M Sport is coming in at 2620 Euro using the VRT calculator. Additional to that is the NOx charge whch was brought in on the 1st Jan, which is calculated as ....
- The first 0-60 mg/km; 5 Euro per mg
- The next 20 mg/km (60-80mg); 15 Euro per mg
- The remainder above 80 mg; 25 Euro per mg

Capped at 4850 for diesels, or 600 for any other type of cars

So, 2620 (CO2 calculation) plus 1475 (NOx charge)

Total to land it of 4095...based on the assumptions above..the CO2 actually shows 114g/km for the one I worked it out on, but unlikely to be much more.
If you want to provide more info like above, I can try get a more accurate calculation.