You start a do loop, but you don't end it. So it only does it once.

$${
IF(autousing);

LOG("&2[AutoFarm] &fStopped.");​

UNSET(autousing);​

STOP();​

ELSE;

LOG("&2[AutoFarm] &fStarted.");​

SET(autousing);​

DO;​

KEYDOWN(attack);​

KEYDOWN(forward);​

LOOP;​

ENDIF
}$$

 

$${
IF(autousing);

LOG("&2[AutoFarm] &fStopped.");​

UNSET(autousing);​

STOP();​

ELSE;

LOG("&2[AutoFarm] &fStarted.");​

SET(autousing);​

DO;​

KEY(attack);​

KEY(forward);​

LOOP;​

ENDIF
}$$

You have to use KEY instead of KEYDOWN