Redmine

I know we can click on User's link and see his activities but I want to add filter on the activity page. One line code below creates a dropdown list which list all the users. I want help with the code. If anybody can help me with redirecting the links to user's activity page when we select any user from the list.

<%= collection_select(:user, :id, u d, :id, :lastname, options ={:prompt => "--Select a User--"}, html_options = {:name => "users"}) %>