Changing Keys might get "Duplicate Hotkey" Conflict but you can copy this / paste in notepad / save as all files with extension .ahk /then install Autohotkey & run the script 

Code:
Hotkey, *$LButton, Rapidfire
Hotkey, *$LButton, Off
*F1::
If !Toggle
{
Tooltip, RapidFire ON, 0,0
Hotkey, *$LButton, On
}
Else
{
Tooltip, RapidFire OFF, 0,0
Hotkey, *$LButton, Off
}
Toggle := !Toggle
Return
Rapidfire:
Loop
{
SetMouseDelay 10
Click
If (GetKeyState("LButton","P")=0)
Break
}
return







