
Thanks for the good question. The answer is unfortunately that there's no way to limit the choices in a link-to-parent record to include only a subset of the parents. We do have this on our product roadmap -- so you could put a filter on the link-to-parent field that limits the choices. I don't have any ETA for when that will be done.
The best work-around in the meantime is to change the calculated field in the parent to indicate invalid choices clearly, and put them at the end of the drop-down list. For example, if your formula is currently Last Name & " " & First Name, and you only want records with a status of "available" to show up, the parent formula could be:
if(not(status = "available"), "zzz - don't choose - ", "") & Last Name & " " & First Name
This will put a "zzz - don't choose" in front of each invalid choice, which not only indicates to users that they shouldn't select that choice, but also moves them all to the end of the list.
I admit it isn't elegant, but it works, until we get a chance to implement the feature mentioned above.

HA! Pretty clever Kevin.

Couple extra goodies with summary views:
1) You can sort a summary view by clicking on the column headers (like all of our views). So if you want to see which company Bill Bower sold to most, just click Bill Bower to sort the summary by his values.
2) On the Display Options tab of the Edit View page, you can set options that are used in summary views (like all views). So in the screenshots above, you can get rid of the two digits after the decimal point (so it says $90,985 instead of $90,985.00).
3) You can email these summary views, or set up automatic email distribution schedules for them, or publish them to a website. Just like with other view formats (except Maps, actually; those can't be emailed or published to a website, alas). So get your morning pivot table by email every day.
More details are explained in the Help article about summary views. We'll try to get that cross-posted in this forum.

I think he should be called "smurf" instead of Blue Icon Guy.

