Adding it would take just as long as game genie codes, I'm not sure if you can create your own cheats with the console PAR, you know the addresses by using a program to search for certain values.

Let's say I've got 10 lives. I tell the program to do a 1-bit search for 10. It finds however many addresses. Now I die to change my lives to 9. Then I tell the program to search through the previously found addresses for the value 9. I just keep doing this until I've got 1 value left, change the value to 255(FF) and presto.

To find out why FF=255 just read up on hexadecimal.