how to make function Keyup working too by give value by another keyup in diffrent entering

how to make function Keyup working too by give value by another keyup in diffrent entering

Hello Guys, i have form that is more complex for me, a lot of jquery function on it,
so here is my simple demo http://jsfiddle.net/dauruk0512/524LpL8r/9/


There is two way buy product

  1. If serial number entering automatically qty has default 1 and cannot edit cause i make readonly
  2. if serial number not entering user can buy product more than 1
Problem is when user doesn't entering serial number then buy same product more than stock i'm success make alert but when user buy entering serial number i cant make alert it, what should i do cause in this function  i  give some event but not working too
  1. $(document).on('keyup, change, blur', '.qty', function() 
 What should i do to make keyup working too, Thanks a lot for any respon guys