How to Select "Null" in combobox filter?

[CrystalSurfer]

I have a listbox on a form displaying records which can be filtered via a number of comboboxes.
These comboboxes allow the user to select "<ALL>" or a specific value from the list. It all works perfectly.

However, I would like to be able to select a filter value of "Null" on one of the comboboxes which would display those records without a value in the relevant field.
How can I do this?

The following (simplified) code is what I'm using:

SQL for the results listbox:

SELECT qryClientSearch.ID, qryClientSearch.Name, qryClientSearch.AccountManager, qryClientSearch.AccountMgr
FROM qryClientSearch
WHERE 
(
((qryClientSearch.ID) Like fCboSearch([Forms]![frmClientSearch]![cboSearchName])) 
AND 
((qryClientSearch.AccountManager) Like fCboSearch([Forms]![frmClientSearch]![cboSearchAccountMgr]) Or (qryClientSearch.AccountManager) Is Null)
)
ORDER BY qryClientSearch.Name;

SQL code for the combobox filter:

SELECT qryStaff_All.ID, qryStaff_All.Nickname FROM qryStaff_All 
UNION 
(SELECT "*" AS ID,"<ALL>" AS Nickname FROM qryStaff_All) 
ORDER BY qryStaff_All.Nickname;

VB Code in Combobox Search Function:

Public Function fCboSearch(vCboSearch As Variant)
    If IsNull(vCboSearch) Or vCboSearch = "" Then
        fCboSearch = "*"
    Else
        fCboSearch = vCboSearch
    End If
End Function

For those that have noticed I have a "Or is null" criteria on the AccountManager field in the result set. I want to take this out and allow the value "Null" to be selected on specifically.

Thanks.

 

[mhartman]

Hello:

This may be of some help:
http://support.microsoft.com/kb/208707/en-us

Regards
Mark

 

[CrystalSurfer]

Thanks for your reply Doc Data, but I don't think that will help.
I think the problem lies in the "Like" criteria in the result query because how can it check both for a specific value (ie "Like 9" or "Like *" ) and then also check for Null values (ie "Is Null") ??? - which is what I want.