Webservice for filtering data in gridview on dropdown list item select

Question

hai all,

 i have a page in which i have a grid view and i have a dropdownlist for filtering, when we select a item from drop down list the data should be filtered and it should be binded to the grid view and display according to the item selected in the drop down list. how can we do this using webservices can anybody help it is urgent.

thanks.