Claire:

Lets take a simple example.  Say you have a table Contracts with columns
amongst others of contacted (a numeric primary key), contracttitle (text) and
your closedate column (date/time).  To get the form to show only those rows
where the closedate column is Null you'd base the form on a query:

SELECT *
FROM Contracts
WHERE closedate IS NULL
ORDER BY contracttitle;

The combo box in the form's header to enable you to select a record by
contacttitle from all non-Null closedate contacts would have a RowSource
property of:

SELECT contractID, contracttitle
FROM Contracts
WHERE closedate IS NULL
ORDER BY contracttitle;

The properties of this combo box would be:

ControlSource:    leave blank
BoundColumn:    1
ColumnCount      2
ColumnWidths    0cm;8cm    or rough equivalent in inches

The first dimension of the last property must be zero to hide the first
column, the second dimension isn't crucial so long as its at least as wide as
the control.

In the AfterUpdate event procedure of the combo box put the following code:

   Dim rst As Object
   
   Set rst = Me.Recordset.Clone
   
   rst.FindFirst "contractID = " & cboFindContract
   Me.Bookmark = rst.Bookmark

where cboFindContract is the name of the combo box.

When a user selects an item from the combo box the code will execute and
find the matching record in the clone of the form's underlying recordset.  It
then sets the form's Bookmark property to that of the recordset clone, which
moves the form to the first matching contractID.

You can add an extra refinement by putting the following in the form's
Current event procedure:

Me.cboFindContract = Me.contractID

This keeps the combo box in sync with the form if the user navigates to a
different contract record with the built in navigation buttons or the
keyboard.

Ken Sheridan
Stafford, England