Killing a process from asp.net page

I have an ASP.NET page which invokes excel, and I intend to kill this excel process once the program has completed creating the reqd excel spreadsheet

I have the following code so far, when I try to kill the Excel process it states Access denied.
I am running the website under a given user account, which has administrative privileges.
My question is why can't I kill the process.


msBook.Close(false, msobjOpt, msobjOpt);

        msBooks.Close();

        msXL.Quit();        

        try

        {

            Marshal.ReleaseComObject(msXL);

            msXL = null;

            GC.Collect();

        }

        catch (Exception ex)

        {

        }

        //Kill older Excel processes

        try

        {

            Process[] p = Process.GetProcessesByName("EXCEL");

            ////kills all processes older than 15 minutes

            for (int i = 0; i < p.Length; i++)

                //if (p[i].StartTime.AddMinutes(2) < DateTime.Now)

                p[i].Kill;

        }

        catch (Exception ex)

        {

        }