This is the script i use for mouse button 4 and 5.
$XButton1::
keywait XButton1
Onetoggle := !OneToggle
While (OneToggle)
{ Send, 2
sleep, 100
}
Return
^!s::
Suspend, Permit
Suspend, Toggle
Return
$XButton2::
keywait XButton2
Onetoggle := !OneToggle
While (OneToggle)
{ Send, 3
sleep, 100
}
Return