I need to know how to enter a new headline every time the first field in a ListBox changes.

My output looks like this:

1 56743 $1200
1 64564 $5400
2 56456 $7853
3 98798 $5645
3 54564 $5456
4 98798 $5645
ETC..

SO how do I enter a new headline any time the 1,2,3 or 4 change.
This is being displayed in A LISTBOX.
Thanks,
Ben