Problem converting durations

[Nelsonk32]

I am converting 8000 rows of data in excel. I am trying to figure out duration of different types phone calls. I converted the info from a .txt file. The only problem is my data is only m:ss, h:mm:ss, or mm:ss. for example it is displayed exactly like this in text 5:34 (m:ss), 1:03:33(h:mm:ss), and 21:34(mm:ss). I tried converting to h:mm:ss and it converts anything more than ten minutes to 10 hours and the hours are changed to minutes. For example using the above numbers 21:34:00 and 1:03. The only way I can get this stuff to look right is to not even format the durations. But I don't know how I'm going to add them without formatting it. There are several different callers and I have to figure out the duration of each. Is there a way I can add the data together if it looks like this 5:34, 21:34, and 1:03:33.

Thank you kindly,

Nelson

[JBeaucaire]

Maybe.... put this in D3, then copy downward:

=IF(LEN(C3)=5, B2+(C3/60), B2+C3)

...formatted as [h]:mm:ss