Insert Query Fails (if Form Fields Left Empty)

Dear All,

I have created a table in my SQL server database, the problem i am facing is my insert query fails if i leave any form field empty (leave it blank). On my back-end table, only one field is mandatory, and others have been set with the constraint "allow null".

As per our business requirement, except one value is complusory while others are optional. If I enter all values in the form it works perfectly fine. Can you see in the code below - where am i possibly going wrong ?

<script language="VB" runat="server" >
  
   Sub Page_Load(Src As Object, e As EventArgs)
     
       
        If Page.IsPostBack Then
           
            Dim ConLath As SqlConnection
            Dim comLath As SqlCommand
            Dim insertcmd
           
            conLath = New SqlConnection("Data Source=SQLas;Initial Catalog=settle;User ID=sa;Password=password")
            ConLath.Open()
            insertcmd = "Insert into His_set values (@t_d,@s_p,@p_s,@v_oq,@i_oq,@v_qn,@i_qn,@v_qw,@i_qw)"
           
            comLath = New SqlCommand(insertcmd, ConLath)
           
           
            comLath.Parameters.Add(New SqlParameter("@t_d", SqlDbType.DateTime, 12))
            comLath.Parameters("@t_d").Value = trade_date.Text
            comLath.Parameters.Add(New SqlParameter("@s_p", SqlDbType.Decimal, 8))
            comLath.Parameters("@s_p").Value = sett_price.Text
            comLath.Parameters.Add(New SqlParameter("@p_s", SqlDbType.Decimal, 8))
            comLath.Parameters("@p_s").Value = post_close.Text
            comLath.Parameters.Add(New SqlParameter("@v_oq", SqlDbType.Int, 8))
            comLath.Parameters("@v_oq").Value = vol_oq.Text
            comLath.Parameters.Add(New SqlParameter("@i_oq", SqlDbType.Int, 8))
            comLath.Parameters("@i_oq").Value = oi_oq.Text
            comLath.Parameters.Add(New SqlParameter("@v_qn", SqlDbType.Int, 8))
            comLath.Parameters("@v_qn").Value = vol_qn.Text
            comLath.Parameters.Add(New SqlParameter("@v_qw", SqlDbType.Int, 8))
            comLath.Parameters("@v_qw").Value = vol_qw.Text
            comLath.Parameters.Add(New SqlParameter("@i_qn", SqlDbType.Int, 8))
            comLath.Parameters("@i_qn").Value = oi_qn.Text
            comLath.Parameters.Add(New SqlParameter("@i_qw", SqlDbType.Int, 8))
            comLath.Parameters("@i_qw").Value = oi_qw.Text

           
            Try
                comLath.ExecuteNonQuery()
               
            Catch ex As SqlException
                If ex.Number = 2627 Then
                    Message.InnerHtml = "ERROR: A record already exists with " _
                       & "the same primary key"
                Else
                    Message.InnerHtml = "ERROR: Could not add record, please " _
                       & "ensure the fields are correctly filled out"
                    Message.Style("color") = "red"
                End If
            End Try

            comLath.Dispose()
            ConLath.Close()
           
           
           
           
        End If
   End Sub

</script>