Beat Detective Question

[slangification]

I've been wondering about this for a long time:

How do you learn the tempo of a loop without generating bar|beat markers?

I've been using a (bad) workaround, but I know there must be a better way.

Here is how I've been doing it. I get drum loop A (which for this example is 2 bars, neatly trimmed kick drum to kick drum), and use beat detective to generate bar|beat markers. So, now I have a grid at, say 100 bpm. Then I have another loop (drum loop B) that is not at the same tempo; it's much faster, and I want to use Serato Pitch 'N Time to make it 100 bpm. For this, I need to know the exact tempo of drum loop B. So, I move it about 30 seconds beyond the current end of the song, and I use beat detective to generate bar|beat markers. Then, since I now know the tempo, I can correctly process in Pitch 'N Time.

The problem with this method is not only does it seem to be more involved than necessary, but I wind up with a lot of messy bar|beat markers, and often (here is the big problem) for some reason it messes up all my other bar|beat markers (and thus the whole song), whether they occur before or after the new bar|beat markers.

Surely there's a better way. Can someone clue me in?