For example, this text:2:263:043:145:384:1210:306:296:5311:499:334:177:496:106:046:286:404:21(These are actually minute:second format, not hour:minute, if it matters.  So ideally the sum would compute hours from the total minutes and give the answer hours:minutes:seconds.)I know there are ways to do this in bash, e.g. with awk.  Running an external shell command is okay, but it has to work from within viand a vim-native approach would be preferred.
How to replace a list of numbers (or times/timestamps) with their sum?
search;replace
One powerful function of vim is piping an area thru an external command.(I think this is not what you are looking for, but, just for the record)::%!awk -F: '{a=$2*60+$1} END {printf(\%d:\%02d,a/60,a\%60)}'\thanks{Wildcard} for pointing out the 10:09 problem and solution