As far as I know, it is currently not possible to loop through a list of tracks and automatically execute a query for each one. One reason is the current Websource possibilities and another reason is the high risk of not receiving the correct information if you only search with ARTIST + TITLE.
Most online sources list many versions of a TITLE for the same ARTIST. These can include the first release on Vinyl, a different release on CD, a release on a later compilation, a release for specific countries only, and so on. I cannot imagine how a fully automated process could select the correct online track that matches your local copy 100%.
See also here.