Cross Browser - Site Mobile Phone Support?

I need to make my site work well on a blackberry, i haven't put too much effort into getting this working yet, but i have a few questions which google is struggling with.I've read about detecting brower type and modifying the default behaviour of asp.net controls hereHow would I go about supplying a differant stylesheet to a specific browser, should i just do this?

if (Request.Browser.Browser.ToString() == "blackberry") //pseudocode
{
Response.Write("bb.css");
}
else
{
Response.Write("bb.css");
}

This will work fine, but i feel like there is a better method, i'm sure i've read about something in the past but i can't seem to recall.I'm also considering a response.redirect to a differant page for a blackberry, which at the moment i would implemenet in a similar way.