High level question:

My Item List has several entries for both HST collected and for ITCs, but they both flow into account 23310, HST on Sales. 

How do I reassign the ITC Items (only) so all ITCs flow into a separate account, 23320, HST ITCs?

Background:

Am using Desktop Premier. I want to have the HST collected flow into one GL account (23310), and the ITCs into another (23320).  This will more easily allow a reasonability test on the two balances (eg. the 23310 movement each month should be 13% * my monthly sales; it's a bit more fiddly to back out the non-HST items from expenses, but the principle's the same to test the 23320 movement.)

Once I've tested both, I file the return using the CRA website, i.e. I don't use the QB menu Sales Tax > File Sales Tax), then journal the amounts to the Receiver General payable.