I have a TIB_LoopupCombo on my form which is linked via a datasource
to a query with the follwing SQL:

SELECT CONTACT_ID
, FIRSTNAME
, LASTNAME
FROM CONTACTS
order by lastname, firstname

I also calculate a field called 'FULLNAME' which is
firstname+lastname.

Now, my problem is trying to make the lookup combo display FULLNAME
only. The combo has it's datasource set and the displayfield is set
to FULLNAME, but when executed, the drop down displays all four
fields: Contact_Id, firstname, lastname, fullname.

Setting the DisplayField to 'FirstName' gives the same result - all
columns are displayed.

Two other Lookupcombo's on the form behave normally, but they don't
use calculated fields.

I've compared the properties of the working Lookupcombos with the
incorrect ones and the only differences appear to be the datasource
and the DisplayField.

Any ideas?

TIA