Listen on axWebBrower.CommandStateChange event.
The event has two parameters:
1) command (int): UPDATECOMMANDS = 0xFFFFFFFF,
NAVIGATEFORWARD = 0x00000001,
NAVIGATEBACK = 0x00000002
2) status (bool): the status associated with the command
Say, If command=0x00000001 and status=false, then you can't go forward any more. The same applys to backward.