you can't, thats not difficult its impossible. because if you read the page rank algorithm, it will should you that you need hundreds of thousands of links to link to you. And you try and get that many in 2 or 3 months google will catch onto you, that you are trying to force link to your sites and will penalize you. Its a slow process that you have to work on over time. Hey if you need anymore help on this subject or needs backlinks let me know. I can get you as many as you want for a decent fee but creating them too fast is a bad idea.
Even if your site becomes PR7 site, and stop paying for the back links from other PR6+ sites, the PR of your site will then drop back in next PR update.