Pass variable through include url

Well,
I have made a template which shows the header.
Now in an empty page I include it on the top and this way it shows when I query the page also the header.
This works.
Now I want in the header there is a cell which is empty to show a message.
This message is dynamic, so it depends on what you give as message.
I could it make that when I query index.aspx?message=test that in my header(header.aspx) it shows the message test.
Now want to do it this way.
I query index.aspx
but in index.aspx I do an include this way:
<!--#include file="template/header.aspx"-->
that I make it this way:
<!--#include file="template/header.aspx?message:test"-->
this way I can show on my header a message in that empty cell without the user seeing it in the url.
Is this possible?

Eeek...
You're really going about this a hard way.
If you aren't using 2.0 (which I'm assuming you aren't) then I'd create the header as a UserControl.
Then just plop it on the page. You can easily create a Public Property on the header then, that is accessible from the page, that you can set the Text to...