you have to do it in code.  you could define a string to hold the bits
of your query and then evaluate the pieces, adding criteria to your
query the user chooses values.  if you're using a multi-select listbox
for query criteria, you don't have any choice, because .ItemsSelected
is a collection, and you'd have to iterate through it to get the
individual values anyway.

Basically, you want to use default values.  In Access, a default value
would be a wildcard like *.  You could write a sql string something like
this:

Dim strSql As String, strParam1 As String, strParam2 As String

strParam1 = "'*'"
strParam2 = "*"

strSql = "Select * From tbl1 Where fld1 Like " & strParam1 _
& " And fld2 Like '" & strParam2 & "'"

for fld1 I will set the datatype as numeric, fld2 is text.  Datatypes of
the Text type require single quote delimeters, but Numeric datatypes
don't require single quote delimeters.  However, the wildcard * does
require single quote delimeters if used by text or numeric flds.  In
fld2 I hardcode the single quotes into the sql string.  But for fld1 I
will place the single quotes inside the strParam1 var.

Since VBA allows late binding, you can replace the value of strParam1
with a numeric value if needed.  The default value is '*' for strParam1,
for strParam2 it is * (no single quotes since the single quotes are
hardcoded in the sql string already).  

So if you have 5 listboxes, you would have strParam1...strParam5.
Depending on the datatypes (Dates would also be numeric) you assign the
default values.  If a user picks a value from any of the listboxes, you
assign that value to the corresponding strParam.

HTH
Rich