ASP.NET Custom Validator Example

In my current project, I had a need for advanced validation on some "fiscal year" textboxes. My client needed the textbox to be able to either accept a year (1980) or a back-to-back year range (80-81). After first trying to do the validation solely server side (eliminating the validator all together), I decided that if I wanted the site to be consistant in it's methodology behind validation, I needed to buckle down and tackle the <asp:CustomValidator />.