Custom validator not working

I have almost the same code in my page_load as I do in the custom validator. It seems as if the custom validator is completely unneccessary because it isn't displaying an error if the user types in the wrong information. Is there a way I can just put the error message in the page load that will make it work?
In debugging mode, Visual Studio tells me that the CustomValidator will never be hit. Not really sure why, but can someone help me figure this out? I really need that error message to show!
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load If Session("IB") Is Nothing Then 'show textbox IBText.Visible = True IBTextBox.Visible = True IBTextBoxButton.Visible = True Else 'hide textbox IBText.Visible = False IBTextBox.Visible = False IBTextBoxButton.Visible = False lb ...