HiAssign priority from 0 to 100. Nets with higher priorityare routed first.Restriction: PADS Router does not use the priority value.This rule applies only to SPECCTRASha
In Tools > Options > Strategy you can define the routing order.
Klaus is correct (as usual), and to answer the rest of your question, you can select just the nets you want (your DP's for example) and just route those. Then protect them. Then route the rest of the board.