If you don't mind not being able to scroll things (i.e. Navigator window, etc.) then one can copy paste the code below to remap the scroll wheel altogether. I think this is simpler as this will work no matter how many charts are open and also offline charts.
Inserted Code
#IfWinActive ahk_exe terminal.exe
WheelUp::
Send {NumpadAdd}
Return
WheelDown::
Send {NumpadSub}
Return 1