Question : ASP.NET CreateUserWizard Custom Validator

In my CreateUserWizard, I added a dropdownlist and a textbox.

The dropdownlist ask the users how they learn about my company. The options are:
0. -
1. Friend
2. Google
3. Yahoo
4. Others.. Please specify

I need a custom validator that will do the following:
1. Make sure that the value of the dropdownlist is greater than 0
2. If the value of the dropdownlist is 4, then the user must provide the answer in the textbox.

Thanks.

Answer : ASP.NET CreateUserWizard Custom Validator

Have u tried this:
var DDLName = document.getElementById('CreateUserWizard1_CreateUserStepContainer_ddIS');

or may be this:
var DDLName = document.getElementById('<%=CreateUserWizardStep1.ContentTemplateContainer.FindControl("ddIS").ClientId %>');