Very complex IF syntax needed - place commas based on the location of another char.

Hello all! I am new to Excel and have been charged with analyzing some call times for the local ambulance squad. Number of minutes elapsed between dispatch, their answering, their responding to the scene, time spent on scene, etc.

I have a spreadsheet with two fields, date and one that contains all of the crucial data, like this:

10:00:009:53:5810:13:039:48:58201/3/2010
9:23:579:38:449:19:503410/22/2010

I am pretty certain that, based on the location of the colons, Excel can put a comma between times so that I can separate these values into their own fields, right? The above examples ideally should be transformed into:

10:00:00,9:53:58,10:13:03,9:48:58,201/3/2010
9:23:57,9:38:44,9:19:50,3410/22/2010

Everything after the two digits after the very last colon can go away, I don't care about it. In other words, in my examples, 201/3/2010 and 3410/22/2010 will be scrapped. I just need to parse left to right and insert commas after the pattern :##:## (colon two digits colon two digits).

What should I do?

Thanks in advance