Hello Adele,
Look at the U.S. Newspaper Project's website. Their goal is to microfilm existing copies of all known newspapers, by state. At least one repository is identified for each state (LSU for Louisiana newspapers).

There is one for New Jersey, AND they may have interlibrary loan. You will probaly have to go to a local repository or State Archives, but many larger libraries should be able to enter the request.

Of course, this is not the onine version you requested. Depending on the years you are searching, those copies may NOT yet be available online.

Some newspaper extracts have been posted online for other newspapers - check the Mercer County NJ rootsweb site to see if the Trenton Evening News is one of those with online references.