Doing that to an exacting measurement is extremely difficult / nigh on impossible, to the extent that the work involved in doing do would be a right royal pain in the arse. Doing it with 1 campaign is pretty much impossible.

I have however done this before, not sure it was worth the effort but here is how I did it.

1. create a seriously well spun article

2. create an ULTRA SPUN paragraph containing links

3. Create a manually spin list of links and keywords for ALL the urls

When the software submits it will average out at a link per url but it is NOT exact. However a single nuke link is as useful as a chocolate fireguard so you would need a few links to each url and then get them indexed for it to really have an effect. Ironically this whole process is quite a handful but a great way of looking far more natural than a big website have lots of links to just a handful of urls.

This is extremely useful in ecommerce website with a large inventory

Rudi