Time duration calculation

Any help on this would be MUCH appreciated!

What I am trying to accomplish is basically, determining the time duration between a start and end time value relevant to a given Record id and Source entry.

The formula would need to identify matching Record ID's, then determine if the Record ID is associated with a BEGIN or END Source so that the Duration between the two can be calculated.

There would also be circumstances when the BEGIN time would not be on the same sheet as the END time. It would be ideal if those particular entries could be flagged with something like "NO MATCH". This would tell the user that they would need to look at a previous sheet to get the BEGIN time info needed.

I have attached an example sheet to hopefully help with the explanation.

Thanks.