I think the vfp scollbars are in its IDE and cannot be traversed.
the mouse parameters can be adjusted in windows section (control panel)

maybe you must know some usefull shotcuts working with editor , form designer...
added to arrow up+arrow down, there is pgUp and pgDOwn and many others.
try this snippet in command window selection+return or in a prg (simply to access to the specific help).
to see "Keyboard Shortcuts (Visual FoxPro)" section in foxhelp

help Keyboard Shortcuts 
local oshell
oshell=newObject("wscript.shell")
oshell.sendkeys("{ENTER}")
oshell.sendkeys("{DOWN}")
oshell.sendkeys("{ENTER}")
oshell=null

can apply these shortcuts
CTRL+DOWNARROW Scrolls window up without moving cursor.
CTRL+UPARROW Scrolls window down without moving cursor.
CTRL+LEFTARROW Moves the cursor one word to the left.
CTRL+RIGHTARROW Moves the cursor one word to the right.