hypermega, thanks for the clarification. I think Suzy summed it up well with "Yuk" ;)
My first thought was whether behaviours might be a way around this as well. I'd just add a couple notes to Suzy's technique. The first is to wrap everything in a conditional comment. It is only a few bytes extra code, and will keep all this away from other user agents. You commented earlier you are linking to an external stylesheet - as that will stop all other downloads, if the amount of code is small you might consider wrapping an inline style sheet (not inline styles) inside conditional comments as well. The final thought was whether an .htc might be a work around. Redundant now as Suzy's solution probably does what is required, but might be a way around other issues in the future.
Suzy, one of us has to stop thinking along similar lines - it gets scary ;)