The root problem is totally solvable, although you might want to look at it from a different angle.
Let me restate your example, and then I'll put a new twist on it:
You have a page, BH1, which directs traffic to another page, BH2, which does its iframing magic, etc. However, BH2
also gets legit traffic from somewhere else. Currently, when the legit traffic comes in, BH2 then redirects to yet another page, WH1, and does whatever it does, but without the iframing etc.
What I am wondering, is why redirect at all? If the traffic is hitting BH2 anyway, then just put
both pages in one PHP doc, and use the referrer to switch which page gets rendered. No redirect, but each traffic set gets its own version of the page. Additionally, to my way of thinking, there is less of a chance of having someone look at the link in your WH traffic, and compare it to the final destination, and ask questions about what is happening in the middle.
If I'm missing something obvious about your method, and why the redirection is essential, let me know. I've been developing sites for a long time, and have done a lot of IM Websites (for others), but have recently decided to see if I can get a seat at the table instead of taking scraps off the floor. Thank goodness I came across BHW, but it still makes me feel like a noob all over again.