Not with PHP, that's for sure. Maybe with Javascript, but then I'm just guessing.
Maybe you should try again to convince your client of not using it. I, for one, never heard about that font in my life. Probably 95% of all visitors will have to download the darned font, so just make the download option visible to everyone. You know, like those horrible sites that demand that you install Flash or Shockwave before letting you in.
Whenever I see one of those, I just walk away...
Luciano ES
Santos, SP - Brasil