Please do or pm me it. For the sake of my finger. Thanks!
Code:
F1::
alt := not alt
if(alt)
{
Click down
}
else
{
Click up
}
F1 is the key you press once to start mining, and press again when you wish to stop. You can change it to whatever you want (AHK gets priority over games so in Starbound for example F1 that would normally hide the GUI is not used); letters/numbers are best avoided because it'll start pressing LMB if you use them to type into chat.
And of course you'll need AutoHotkey installed, you can either make a new .ahk file with Notepad or just use the default one: right click the AHK logo on taskbar, 'Edit this Script' and paste the above. Then save and 'Reload this Script' and pressing F1 should start holding your left mouse button down.