>Thanks Dragan! The other suggestion that I'm getting is to have them do the data entry only in the vocative case.
>
>But Lucie (my Czech colleague) says that that is nonsense because the address on envelope has to be in the nominative case.

Address should be in nominative - the vocative would be needed for merge letters, where you may be addressing the person. And even there you may get away with clever wording - maybe having an Attn: field, and lower just address them with "Dear sir" or whatever phrase the "pan" may get into.