or you can try this (simple script editing):
if(message=="~xy")
{
uint16 hexX=0, hexY=0;
GetMonitorHex(__MouseX, __MouseY, hexX, hexY);
Message("Hex: "+hexX+" "+hexY);
return false;
}
If you add it into client_main.fos right behind the if(message[0]=="~names"){...<somelines>...} block.
Then everytime you type ~xy you will get X Y coordinates of your mouse. (There are more elegant ways to deal with it, but this is one of the simpliest)