Many thanks kg4wsv. Your simple example has helped me greatly. I tried your method of passing the byte value of the output pin number to the led argument in the function - and it works a treat! Also, reading the Arduino reference, this method of defining fixed values at the beginning of the code (using: #define constantName value) saves on chip memory space!! Not only that, it allows the value to be used as a byte (so long as it is between 0 - 255) all in one hit. I guess this would have been easier if I knew the C Language. I wasn't completely aware until now how close the "Arduino Language" and "C" really are! What areas of the C Language are not supported?