Post data from selected feature to an aspx web form on another site using Web Request activity

Does anyone have a workflow that I can take a gander at that uses the Web Request activity to post data from a selected feature into an aspx web form on another website? This is way over my head but what I would like to do is take the parcel number from a selected feature and post that into a web form on the Tax Assessors website in order to get sales information. Normally I would just set up a parameterized URL to query the parcel in their database but this is not possible the way they have their site set up. As soon as you enter the parcel number into the form on their site, it pulls up the related parcel info. I just want to be able to select a parcel on my site, hit a hyperlink, and have their site open up in a seperate window with the related parcel already pulled up. Right now I have to copy and paste the parcel number from our site into their form and it would be nice if I could just have more funtionality between their page and ours.