Yep, you would need a new scanner that does trunk tracking.
Talk Groups (TGs) and Talk Group IDs (TGIDs) are only usable on a scanner that does trunk tracking. As rpowley
wrote, you would have a hard time trying to listen to a Trunked Radio System (TRS). Each time a user talked, the control channel could change the frequency to another frequency in the system. This could happen every time the users key up the radio and transmit (or it could happen less frequently, but it still would happen). On a TRS with only a few frequencies, this would not be too hard to track using a scanner that does not have a trunk tracking feature. However, this is not always the case and there would be too many frequencies to really quick try to catch to keep up with a conversation. To really compound the issue, if there was more than one conversation going on by different users, it would be very difficult to be able to track who was saying what to whom. There could be several users talking to each other all on the same system and the system keeps rotating the frequencies randomly.
I suggest buying a new scanner, one that is capable of trunk tracking. You can pick on up at a relatively low cost if you are not interested in all the bells and whistles and you don't need it to decode APCO P25 (which is another subject altogether). You could even get a used one from eBay or elsewhere.
Sorry about the not so good news.