HL7 message

I've used following code to generate HL7 message


{
 // show generated string
        // retrieve a datatable with all required data from database

        SqlConnection sqlcon = new SqlConnection("server=test; database=Lab; uid=sa; pwd=sa");

        string sqlcmd = "select  (substring(clinic,4,1) + substring(clinic,2,2) )as clinic,[External Code] as pid, firstname, lastname, test, result from Patients a inner join Lab_result b on a.[external code] = b.MRN order by PID, draw_date";



        SqlDataAdapter sqlda = new SqlDataAdapter(sqlcmd, sqlcon);
        DataSet ds = new DataSet();
        sqlda.Fill(ds, "Patients");
        GridView1.DataSource = ds;
        DataTable dt = ds.Tables["Patients"];

        // need to add code to set date in correct format

        string curDate = "20060705003913";
        string oldPID = "";
        int msgCount = 0;


        System.Text.StringBuilder sb = new System.Text.StringBuilder();

        // build file headers

                sb.Append(@"FHS|^&\~|4||hhh ver. 3.4.05|4|20060705003912" + "\r\n");

                sb.Append(@"BHS|^&\~|4||hhh ver. 3.4.05|4|20060705003912||||20060075003912" + "\r\n");
                sb.Append(@"MSH|^&\~|NAPPY|||4|" + curDate + @"||DFT^P03|0|P|2.2" + "\r\n");

                sb.Append(@"EVN|P03|" + curDate + @"||OVR" + "\r\n");

        foreach (DataRow dr in dt.Rows)
        {
         
       
            string PID = dr["pid"].ToString();
         
            string clinic = dr["clinic"].ToString();
         
            // if this is a different patient than the last one, we need a patient header

            if (PID != oldPID)
            {
             

                if (msgCount != 0)
                {    
                    sb.Append(@"FT1||||" + curDate + @"||C|ZZ^Load Lab Results^^"
                         + @"N^N|||1|||" + clinic+"||||||" + "586.6" + "\r\n");
                }


                // and if its not the first patient we need a patient trailer record
                // (need to determine where the A230 value comes from)


                sb.Append(@"PID|||" + PID + @"||" + dr["lastname"].ToString().Trim()
                     + @"^" + dr["firstname"].ToString().Trim() + "\r\n");
                msgCount++;
                oldPID = PID;
            }

            // determine which test it is (could just substitiue test name from
            // database if that's appropriate

            switch (dr["test"].ToString().Trim())
            {
                case "%URR":
                    sb.Append(@"OBX||ST|URR^URR||");
                    break;
                case "HGB":
                    sb.Append(@"OBX||ST|HCT^HGB||");
                    break;
            }

            sb.Append(dr["result"].ToString().Trim() + @"||||||R" + "\r\n");

       


        }

   

       
        // add trailer for last patient and file trailers with patient count
     
        sb.Append(@"BTS|" + msgCount.ToString() + "\r\n");
        sb.Append(@"FTS|1" + "\r\n");
        TextBox1.Text = sb.ToString();

}


How can I repeat the message header every time there is a new PID

MSH
EVN
~~

also, FT1 is not write in the last PID not sure why??  
In the last PID
PID
OBX||ST|URR^URR||54.0||||||R
OBX||ST|HCT^HGB||12.8||||||R
~~noFT1 here
BTS|1123
FTS|1



and how can I binding the clinicID into clinc field in FT1 line?



the output should  looks like
FHS
BHS
MSH
EVN
PID
OBX
OBX
OBX
FT1
MSH
EVN
PID
OBX
OBX
OBX
FT1
---
etc


BTS|1123
FTS|1