ASP.ner Cookie error

[Bantha]

I keep getting thei error and can fin out why

Response is not available in this context.
Description: An unhandled exception occurred during the execution of
the current web request. Please review the stack trace for more
information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Response is not available
in this context.

Source Error:
Line 25: CookieUserID.Expires = Now.AddMinutes(30)
Line 26:
Line 27: Response.Cookies.Add(CookieUserID)
Line 28:
Line 29: CookieUserAuthority = New HttpCookie("Authority")
Source File: C:\Documents and Settings\PASCAL WORK\My Documents\Visual
Studio Projects\ITAssets\APP_LAYER\Security.vb Line: 27

Stack Trace:
[HttpException (0x80004005): Response is not available in this
context.]
System.Web.UI.Page.get_Response() +2025449
APP_LAYER.CLS_Security.Begin_session(Int32 EmployeeID, Int32
Authority) in C:\Documents and Settings\PASCAL WORK\My Documents\Visual
Studio Projects\ITAssets\APP_LAYER\Security.vb:27
ITAssets.Login.BtnLogin_Click(Object sender, EventArgs e) in
c:\inetpub\wwwroot\ITAssets\Login.aspx.vb:56
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
System.Web.UI.WebControls.Button.RaisePostBackEven t(String
eventArgument) +107

System.Web.UI.WebControls.Button.System.Web.UI.IPo stBackEventHandler.RaisePostBackEvent(String
eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEve ntHandler
sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCol lection postData)
+33
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint