An aftermarket electronic circuit has a first data processor and a second data processor, the first data processor adapted to communicate with an imaging machine having a processor associated with a block of memory dedicated for an imaging unit blocking list having at least one blocking position. The second data processor contains blocking data, and the first data processor is adapted to access the blocking data from the second data processor. The first data processor is adapted to provide the blocking data to be read by the imaging machine and written to at least one byte of each available blocking position of the blocking list.