convert hh:mm:ss-hh:mm:ss to seconds-seconds

I am using Excel 2010 and I am trying to convert times shown in the format hh:mm:ss - hh:mm:ss to seconds-seconds. Here is an example, I am doing something with movies, but for editing purposes in need it in seconds instead of the hour:minute:seconds format. For example in need to convert from 00:35:43 - 00:37:10 to 2143 - 2230. Here are are few more examples of what I need to convert to seconds format...
1:30:13 - 1:33:07
1:00:09 - 1:02:57
Does anybody have any idea how I can do this?