Please elaborate your question a little, but I think you can achieve what you want using the Ruby mechanize library.

require 'mechanize'
a = Mechanize.new
url = 'http://genome.ucsc.edu/cgi-bin/hgPcr?command=start'
page = a.post(url, {"wp_f" => 'AAGTCTTCATATCATCCTTGTT', "wp_r" => 'GTAGCTGAACTTGGTTCTTTC'})
puts page.body
puts page.link_with(:href => /hgPcrResult/).href

Please note that UCSC has a poicy against extended use of automated queries: hitting it too hard might get your IP banned.