ASP.NET: HtmlInputHidden = Nothing

[Ma³y Piotruœ]

Hello,
(Sorry for my English, it's not my country language).
I created .aspx page with HTML control:

<input id=CustomersType name=CustomersType type=hidden runat=server>

and I have it declared in behind-code:

Protected WithEvents CustomersType As
System.Web.UI.HtmlControls.HtmlInputHidden

then I made an assignment in Page.Load:

CustomersType.Value = ...

Unfortunatelly CustomersType = Nothing (QuickWatch).
Could you help me to solve this problem (to allow assignment).
Thank you very much.
(MP)