Custom Lists

We are using Netsuite Small Business & have created a custom list to keep track of our serial numbers, the serial number gets added from the PO or Bill and when we sell something, we manually go in & inactive it from the list. I created a custom serial number search which shows all the serial numbers & works great, but I tried to also create a custom search to show only the serial numbers that WEREN'T inactive, but it still shows me all of them.
Is this an Issue or am I doing something wrong?
Thanks
Carrie