So, call checkPin() when z has the right value.
Fine with me 
- but where to call it? i need this to be cut out in cardboard please (don't know if you can use that saying on English)
How would you distinguish "a random button" from entering a character in the password?
Actually i didn't think to much about how to handle that.. If i use your "if test" how hard would i be to implement for a beginner?
Thank you very much, i appreciate your help!