Difference between two times - avoiding ###### for times that span midnight

I'm trying to find the difference between two times in (h):mm:ss format using the most basic of functions (B1-A1) but this creates a problem when the times span midnight as it wants to return a negative number. Any better ideas on how to get around this? The date of the times is not available in the data i have.

Example:

19:32:46 19:34:09 0:01:23
23:46:04 0:00:55 #####
11:07:41 11:57:27 0:49:46
14:24:45 15:32:11 1:07:26
17:03:25 17:03:30 0:00:05
21:29:07 22:18:27 0:49:20
23:48:20 0:30:26 #####
15:29:43 16:43:06 1:13:23
20:11:12 20:41:22 0:30:10
4:50:04 5:34:40 0:44:36
17:46:18 18:15:33 0:29:15
23:20:19 0:36:17 #####
12:36:26 13:36:18 0:59:52

That worked perfectly! Thank you!