Hello.. I am kind a stuck in how to develop a notification code? plz. help me here i m really pissed off , of this prblm

I am developing a matrimonial website so in that customer should get notified whenever his profile got a view all by now I used update query as if

Code:-

string a = e.CommandArgument.ToString();
update viewprofiles set viewprofile='" + Session["id"].ToString() + "' where id='" + a + "'";

but the only prblm here is it the ids get insert in viewedprofile but it get updated or replaced by other id if B views A's Profile so B's ID is getting inserted in A 's data base but if C views A's profile so B's id get replace by C's id. if possible can it get insert in a line like B's id , C's id, D's id, i.e. 1,2,3