Updates, But Doesnt Insert..

Hi,
I have a button with code to update a column in a table, and insert other values into another table.
I currently have it working to update the column, but not insert.
It gives an error message, but still updates the column. It doesn't insert, which leads me to believe the error is somewhere in the insert code..
It isn't giving me any red squiggly lines in the code though, and the error doesn't show where its referring to, just giving a stack trace.. 
Error:
Exception Details: System.Data.SqlClient.SqlException: Incorrect syntax near ')'.
Incorrect syntax near '@User'.
Stack: 
[SqlException (0x80131904): Incorrect syntax near ')'.
Incorrect syntax near '@User'.]
System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +180
System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +68
System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +199
System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +2411
System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +147
System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +1089
System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +314
System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) +413
System.Data.SqlClient.SqlCommand.ExecuteNonQuery() +115
detailproview.ExecuteInsert(String quantity) +452
detailproview.Button2_Command(Object sender, CommandEventArgs e) +79
System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e) +75
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +155
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4886
 
Code:
private bool ExecuteUpdate(int quantity)
{
  SqlConnection con = new SqlConnection();
  con.ConnectionString = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\ASPNETDB.MDF;Integrated Security=True;User Instance=True";


  con.Open();

  SqlCommand command = new SqlCommand();
  command.Connection = con;
  TextBox TextBox1 = (TextBox)FormView1.FindControl("TextBox1");
  Label labname = (Label)FormView1.FindControl("Label3");
  Label labid = (Label)FormView1.FindControl("Label13");

  command.CommandText = "UPDATE Items SET Quantityavailable = Quantityavailable - @qty WHERE productID=@productID";
  command.Parameters.Add("@qty", TextBox1.Text);
  command.Parameters.Add("@productID", labid.Text);
 command.ExecuteNonQuery();

  con.Close();
  return true;
}


    private bool ExecuteInsert(String quantity)
    {
        SqlConnection con = new SqlConnection();
        con.ConnectionString = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\ASPNETDB.MDF;Integrated Security=True;User Instance=True";

        con.Open();

        SqlCommand command = new SqlCommand();
        command.Connection = con;
        TextBox TextBox1 = (TextBox)FormView1.FindControl("TextBox1");
        Label labname = (Label)FormView1.FindControl("Label3");
        Label labid = (Label)FormView1.FindControl("Label13");

        command.CommandText = "INSERT INTO Transactions (Usersname)VALUES (@User)"+
          "INSERT INTO Transactions (Itemid)VALUES (@productID)"+
          "INSERT INTO Transactions (itemname)VALUES (@Itemsname)"+
          "INSERT INTO Transactions (Date)VALUES (+DateTime.Now.ToString() +)"+
          "INSERT INTO Transactions (Qty)VALUES (@qty)"+
        command.Parameters.Add("@User", System.Web.HttpContext.Current.User.Identity.Name);
        command.Parameters.Add("@Itemsname", labname.Text);
        command.Parameters.Add("@productID", labid.Text);
        command.Parameters.Add("@qty", TextBox1.Text);
        command.ExecuteNonQuery();

        con.Close();
        return true;
    }


protected void Button2_Click(object sender, EventArgs e)
{
  TextBox TextBox1 = FormView1.FindControl("TextBox1") as TextBox;
  ExecuteUpdate(Int32.Parse(TextBox1.Text) );
}

protected void Button2_Command(object sender, CommandEventArgs e)
    {
        if (e.CommandName == "Update")
        {
            TextBox TextBox1 = FormView1.FindControl("TextBox1") as TextBox;
            ExecuteInsert(TextBox1.Text);
        }
    }
}


 
 If anyone can help, ill be very grateful!!
 
Thanks!
Jon