I'm not sure why your hotkeys don't work. Have you got another script running that uses the same hotkeys? Or maybe the poker client uses certain hotkeys of its own. Anyway, the code for increasing and decreasing the bet size using ControlClick is below.

Code:
WheelUp::
MouseGetPos,,,win
ControlClick, x%BetBoxX% y%BetBoxY%, ahk_id %win%
Send {HOME}+{END}^c
BT:= clipboard
BT+=BB
Send {HOME}+{END}{Del}%BT%
return


WheelDown::
MouseGetPos,,,win
ControlClick, x%BetBoxX% y%BetBoxY%, ahk_id %win%
Send {HOME}+{END}^c
BT:= clipboard
BT-=SB
Send {HOME}+{END}{Del}%BT%
return