Nec nd 3500ag oem

can i update the firmware on my external nec nd3500 ag oem burner
i have been told it can,t be done so i thought i would ask the experts

Yes you can. I’m not that farmiliar with flashing firmware on the externals (I think it is about the same as a normal 3500) but you can find firmwares and info here. If after you search the forum you cannot find info on how to flash it try posting and asking thier (or pm a mod and ask for this question to be moved to the nec forum).
here is the nec forum