GridView...Problem

I m creating the project in asp.net using c# and vb languages in 2005.
I have used the asp standard controls(with table<td><tr>) and gridview to design the form.
I m using sqldatasource to insert and  update data from sql server 2005.
I have written the following code 
 <script runat="server">
     Private  Sub Page_Load()
        If Not Request.Form("SUBMIT") Is Nothing Then
            srccompany.Insert()
        End If
    End Sub
</script>
   <asp:SqlDataSource
        id="srccompany"
        SelectCommand="SELECT * FROM companymaster"
        InsertCommand="INSERT companymaster(companyname)
           VALUES (@companyname)"
      UpdateCommand="UPDATE companymaster SET companyname=@companyname WHERE companyid=1"
       DeleteCommand="DELETE companymaster WHERE companyname=@companyname"
        ConnectionString="<%$ ConnectionStrings:companymaster %>"
       Runat="server">
</asp:SqlDataSource>   
<asp:GridView
        id="GridCompanyMaster"
        DataSourceID="srccompany"
        Runat="server" />
Please help me to insert the data in sql server.i m not been able to insert the data is there any problem in coding..
Also i m not been able to edit the data and store back to sql server.
Only i can do is i can view the contents in gridview 
Please give me some tips