How to have input for web service page

[hon123456]

Dear all,

I want to create web service which will allow user to input
two values. I do not want
to create asp.net page to have form to let the user input function.
What I have seen is that
when user access demo.asmx . They can have input box in the lower part
of the web service
page. My question is how can I let user input the value in the web
service page when the user invoke web service. May be I need to write
something in the source code of web service. Please
suggest how to do that?

Thanks.