data Grid

Question

hi all,

        in my application i have a grid in which i display name of the persons basing on the login credentials, but i am getting all the names of all the persons in the database on the grid, i created a hidden field to which i assigned the session of the login credentials to the hidden field. but how can i write a query in markup(in datasource of the grid) to display the concern names in the grid can i assign the hiddenfield value to query. how can i assign the hidden field value to the query in markup,
query will be something like "select a,b,c from x where companyid=hiddenfieldvalue"

can any one help me please.