Tracking status of references

Sometimes I have sources that I want that I haven’t yet been able to find, some I have printed, some I have saved as pdf. Is there an easy way to track the status of my references in Endnote? I tried to customize a field but I couldn’t find the field in my PubMed references that I imported and besides it didn’t seem very easy to access the field for updating/changing the status. Any help would be most appreciated!