In the StylePicker you can check out the memo box for any difference between the A and B parts, but you can apply a style change like mentioned previous and set the style or RealTracks to be double time or half time. I've attached a file so you can see how to do it in the StylePicker for the RealTracks listed in the Style.

Attached Files (Click to download or enlarge) (Only available when you are logged in)
halftime-stylepicker.png (123.99 KB, 38 downloads)

Cheers,
Ember