If it doesn't have a manual button, most of them switch by the following key sequence.
Scroll Lock, Scroll Lock (twice in rapid succession)
1-9 (Port number you want.)
E.g.
Scroll Lock, Scroll Lock, 2 (FOR PORT 2)
Some of them also let you do-
Scroll Lock, Scroll Lock, UP ARROW or
Scroll Lock, Scroll Lock, DOWN ARROW
To toggle through ports one at a time.
If that doesn't work, I suggest using google to look up the manual as Belkin is still in business.
-Nyle