I've ran into this type of problem before.

The best I've managed to accomplish is to display
- the years in down the left columns
- the customer # along the top row
- and a count of the records in the data area
By manually viewing this "matrix" of information you can visially see the gaps and years that have orders. By using the drill down on the subtotals you can inspect the records in greater detail. Granted, this method wouldn't work for a large setup of unique customers but should get you through the night on smaller data sets.

I'd be interested if someone else has something else to offer. MS needs to add more functionality to PTs