VB How-to Validation TextBoxes

Question

Hello All I am new to vb. net... just started studying and was going true a sample code about how to validate textboxes... I go the sample code but not the explanation with it... does anyone know where i can find a step by step info about creating that project... and I also want to know that when u create a class inheriting "System.Windows.form.textbox" how do you use that class then ... I mean how do you put that inherited textbox in the form... Anyone who know's this sample project pleassse help me... it's really important as i have to present it Thanks to all who can help... S.m.