I 've been struggling the past couple of days to find how to create and route differential pairs in Proteus v7. Alas no luck.
I had no luck either, at figuring out how to measure track lengths...
I can't except that a software of such magnitude lacks these fundamental abilities.
So I turn to you as my last resort.
I don't think there is a way to measure track length or automatically route differential pairs like in Altium Designer.
Just route the tracks side by side close to each other. Why would you need them to be perfectly the same length? How fast is the differential signal?