Seriously it isn't hard to do if you take the time to learn.
You have the following:
js code:
function OnEvent_ChatWndReceiveMessage(pChatWnd, sOrigin, nMessage, nMessageKind) {
}
You can check if the command is !calc by doing something like this:
js code:
if (nMessage.indexOf('!calc') === 0) {
/* the above if statement checks if the beginning of the message
is !calc.
*/
}
To get the equation you can do something like this:
js code:
nMessage.substr(6);
Then research how to use eval() or figure out how the script does it.