Dear Bud,
Short answer is No
However you could store the three initially identical cardfiles on the one machine (as long as it is ALWAYS ON)You would then have to merge all of them periodically to update each cardfile with any changes that have been made by any of the users (and then SaveAs over each of the other cardfiles).
It is an easy enough thing to do and only takes 10secs or less to merge each one. But and a big but, all the machines that you are merging them on should not have Sidekick running at the time...
I do it all the time at work and it has been grand for several years, as long as no-one alters the Index fields in the cardfile i.e. No FirstNames / LastNames & Addresses in the cardfile are identical (if that is what you sort on).
Good Luck!
Regards Jim
Check the FAQ area of this Forum for answers (If there are any FAQs!) , it could save you a lot of time and effort and means that links are more likely to be current. Please 'Comment' on them if they are not!