You don't say if you have any programming experience at all. So the answer could be different. I think the O'Reilly books have a lot of good information in them but there is a lot of stuff on the web you can also refer to, C# Tutorials are all over the place. You can also search daniweb there is a ton out there already on this subject
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...