Help! Can not run update querry on web from

I am using sql one sql data source to retrieve data to a drop down and then trying to update selected value of drop down to text box using 2nd sql data source . But error comes that " Updating is not supported by data source 'SQLDS_modInstructor' unless UpdateCommand is specified. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code"" Please help. Source code below: Exception Details: System.NotSupportedException: Updating is not supported by data source 'SQLDS_modInstructor' unless UpdateCommand is specified. Source Error: Line 30: Line 31: Protected Sub btn_modInstructor_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_modInstructor.Click Line 32: SQLDS_modInstructor.Update() Line 33: Line 34: End Sub"
<%@ Page Title="" Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup ...