You want to take a look at how HTML forms work. When you hit the submit button the information in the textbox is packed into a url and sent to the webserver by your web browser. All you have to do is make that URL programatically instead of having the web browser generate it.
I am not sure but I think the URL looks something like below
http://www.mywebpage.com/mypage?myTextField=10
Just do a little reading on how html forms work and you should be able to figure out how the information should be placed into the url.
Edit, I saw your new post: What you have to do is submit an html POST request and I believe the url should be:
http://www.thewebpage/page?strname=198
Where 198 is replaced with the score you want to manipulate.
EDIT: Updated the the last edit for clarity.