Hi Shing-Kwei:

Make sure you have "Check Beaming" in the Speedy menu checked to have the beaming follow the time signature pattern. You can also control the global pattern of beams in the Document Options - Beam dialog box. And of course, you can select a region of menu and choose Utilities / Rebeam... to further edit existing music to a specific beam pattern.

Cheers,
Michael Johnson
VP, Professional Notation
MakeMusic