Survey Submission (ASP.NET using VB.Net)

I need help on a component of an ASP.NET project. I am allowing users to login, complete surveys, revisit surveys, and edit their previous responses. I need something that is efficient that will allow me to know when a submit button is clicked, which controls have been changed so that only those controls values will be submitted to the database. The controls I need monitored are checkboxes, textboxes, radiobuttonlists, dropdown lists, and listboxes. Example: User edits the survey (which was loaded from the ms access db), clicks the submit button, a postback occurs and then: Sub Button1_Click(ByVal sender As Object, ByVal E As EventArgs) Dim c as Control For Each c In [login to view URL] If TypeOf c Is TextBox Then If ctype(c, textbox).changed=true (note: this "changed" property is what I need coded) Then do some SQL... For Checkboxlists, multiple things can be checked, so the code would look like this: If TypeOf c Is checkboxlist Then Dim li as ListItem For each li in [login to view URL] If li.changed=true (note: this "changed" property is what I need coded) Then do some SQL...