You can use closed mode when you want to scan a large trunked system and it will not fit into one bank so with a system like seattle you would need to put it into 2 banks and run those two banks in closed mode as i belive seattle has over a 140 channels that they use and a lot more hex codes then, that will fit into one bank. now i am also new to the pro 97, if you use win 97 you will see an opticon where you can put a bank into closed mode.click on the channels list and it will be to the right side of channel tag.
Now this said i have not done this myself i have just read that this can be done, ijust scan the snohomish area and it will fit into one bank i used win 97 and the web import thing to do this and it has worked fine.