Hi Guy,
By "in the same run process" do you mean adding some logic to your job so the node selection happens dynamically or just selecting the nodes you want it to run on at execution time?
Not sure about the first option but the latter is pretty straight forward as long as you've checked the "dispatch to nodes" option and selected an appropriate filter.
If the "dispatch to node" was the droids you were looking for then you might want to read this
http://rundeck.org/docs/manual/jobs.html#node-dispatching-and-filtering
and head to the Dagobah system.
J.