Using custom constants within a VB / ASP.NET site

[Spanks]

I'm adding a test site variant to an existing ASP.NET project written in VB and I'd like to make it apparent to users they are in the test site with a different banner and background etc. I've created a new test configuration and under Compile | Advanced Compile Options I've added TEST_MODE="1" as a custom constant. Then I attempt to use the following code in the ASPX file:\[code\]<%#If TEST_MODE = "1" Then Response.WriteFile("header_test2.htm")#Else Response.WriteFile("header.htm")#End If%>\[/code\]The IDE shows the first statement grayed out and doing a rebuild and deploy it is still including header.htm. I wondered if anyone has ideas on why it doesn't work or can suggest an alternative way to include different files depending on the active configuration.