Let's asume that you want the distance between the two via's of a differential pair to be 0.5mm.
- Create a Netclass "LVDS" for the LVDS signals and add the appropriate nets.
- Create a clearance rule and give it a meaningful name "0.5 mm", set the via to via clearance to 0.5mm
- Add a class - class clearance for LVDS to LVDS and set it to the 0.5mm clearance rule
If you switch layers, the differential via will be placed at the clearance defined in the 0.5mm rule
In the same way, you can control the distance between the differential pairs.
Regards, Charles