upload a file through a remote web page

Dear All
I have a very urgent requirement if somebody can
help!!!!!!!!!!!!!!!!!!!!!!

i have a requirement to upload a file through a remote web page.
Speaking more clearly i have a excel addin that will pick some values
from the cells and create a text file, after that using a web page url
it will try to uplaod that text file. The Webpage consists of a File
control and a Button to Import. Now the above process will be silent
and will be not visible to the user. I have tried with the querystring
using the POST meathod of httpWebRequest, but the querystring does not
provide any facility to specify the file location.

Kindly help
Thanx
shantanu

.