After the fact, you'd have to reassign it with a new value. The other way would be to write the code so that you can create the list of commands with the values you want them to have, rather than change them after a list has been made. Without seeing any code, however, I can only guess at what you're doing.
As for the items not showing, I can think of a few reasons, but again, with no code it's a guess at best. The first guess would be to check that the list containing the items actually has items in it, then to make sure that you are refreshing your contents bitmap properly. I've known a few times where I've had list not update properly and it's always been a simple and silly thing I've forgotten to do.