Hi Alonso,
ASPX templates do not allow to use K# macros in themselves, but you can use full range of our API. So you can either access HttpRequest object with HttpRequest.Browser.Browser and this should provide browser information, or you can use BrowserHelper class like BrowserHelper.GetBrowser().
Both of these can be used within aspx templates and can leverages instead of K# sharp macros(our macros are just wrapping API anyway).