Formula Involving Four-Digit Military Time

In A1, I've got a time for an event expressed in military time without colons, like 1130.

In B1, I've got two more times expressed the same way, like 1230-1300. These are the time the event was actually began and ended.

I've separated these two times into four different columns, the first two (C1 and D1) containing the raw numbers 1230 and 1330, and the second two (E1 and F1) containing those numbers formatted as times (12:30 and 13:00) via the TEXT function =TEXT(C1,"00:00")

Getting the difference between these two times (expressed in minutes) is not difficult. What is proving to be difficult (however simple it seems) is checking to see if C1 (time event began) is within an hour of A1 (time event was scheduled.) I was able to get this to work with times not involving 0000 or having, say, 0130 as an event time and 2300 as the time the event was started, but those two cases (switching 0000 to 2400, and moving between "days") is causing a hangup. Checking if A1