Currency convertor finishing help

[Spinball]

Hi folks,
I don't know how much interest there would be in a currency convertor, but I have written one using Javascript and PHP which automatically gets the latest rates from a European bank.
For the visitors to my forums - who buy DVDs from the US, Canada, Australia and occasionally Hong Kong, it would be a nice feature.
But I only want it to appear in 3 or 4 specific forums.
So what code would I need to put at the top of forumdisplay template (before $forumdisplay[forumslist]) to check the forum ID and if it matches certain numbers, loads in a new templete?

Is this the right way to do it?
Thanks

[mr e]

you'd have to put the code in forumdisplay.php but im not sure where

[Spinball]

Ideally below the list of people browsing the forum.
My code is a mixture of PHP, HTML and Javascript. It works perfectly if I require global at the top.
Integrating into the forums is where I'm lost.