For trunktracking you either enter all the frequencies for one particular trunking site, or in the case of scanners that do control-channel trunking, you just enter the control channel frequencies. For Radioshack GRE scanners (i.e. the Pro 433 or Pro 2055) you enter these frequencies into one "bank". For Uniden scanners you create a new "system".
Once you've done that you can scan the trunked system. From here you have to tell the scanner what talkgroups you want to listen to. In a trunked system talkgroups are what individual frequencies or channels used to be. The decimal number is the numeric id of a talkgroup.
So in your case to listen to Troop C district 2 you would enter talkgroup id 2064. Now the scanner can follow that talkgroup and ignore the others.
Spend some time reading through the WIKI section of this site. It's a wealth of information. As far as the Pro433 one issue is it doesn't support text tags. So you'd have to remember that 2064 is Troop C, District 2, rather than seeing it in the display. I have both Radio Shack and Uniden scanners but I'm biased in favor of Uniden. Take a look at the BC15. It's has a lot more features and I think you can get it for $229 from Universal.
http://www.universal-radio.com/catalog/scanners/0115.html