You can use the same parameter name under multiple date fields. The user
will be prompted once for each parameter.

It gets more messy to return rows where the dates are null. Basically, you
need to:

a) Declare the parameter (Parameter on Query menu), so Access knows its data
type (thus avoiding a bug where JET mishandles nulls with parameters of type
Text.)

b) Construct the WHERE clause so that it returns the records if the
parameter is null, e.g.:
   WHERE (([WotDate] Is Null) OR ([MyField] >= [WotDate]))

This quickly gets very messy where you are trying to handle combinations of
AND and OR and Nulls. An alternative (and more efficient) approach is to
provide a form where the user can enter the limiting values, and build the
WHERE clause from only those boxes where the user entered something. You can
then use the result as the Filter of a form, or the WhereCondition of
OpenReport, or in the RecordSource of a form/report etc. For an example,
see:
   Search form - Handle many optional criteria
at:
   http://allenbrowne.com/ser-62.html

Not sure I really understand... but it may be that you can check the
parameter about being null (not entered by the user) and then, change it for
a default value:

... WHERE ... StartingDate >= Nz(StartingDateParam, #01-01-1901#)  AND
EndingDate <= Nz( EndingDateParam,  Now() )  AND  ....

Here, if nothing is entered in startingDate parameter, January First,1901,
will be taken, etc.

Vanderghast, Access MVP

A little more infomation requested.

Do you want a record returned if any of the four date fields matches the
criteria or do you want all four to match?  From the comment about fields
having null values I would guess the former. The SQL statement would look
something like the following.

Parameters [Enter Period Start] DateTime, [Enter Period End] DateTime;
SELECT *
FROM [Your Table]
WHERE [Sort Start] Between [Enter Period Start] and [Enter Period End]
Or [Sort Completion] Between [Enter Period Start] and [Enter Period End]
Or [Soft Open] Between [Enter Period Start] and [Enter Period End]
Or [Last Day Business] Between [Enter Period Start] and [Enter Period End]

In the design view (query grid), you would enter the criteria on four
different rows

Field: Sort Start
Criteria(1): Between [Enter Period Start] and [Enter Period End]
Criteria(2):

Field: Sort Start
Criteria(1):
Criteria(2): Between [Enter Period Start] and [Enter Period End]

etcetera

As long as the parameter is EXACTLY the same you will only get asked one
time for each parameter. (I usually cut and paste to ensure that I don't
mistype.)

Also, to make sure that Access understands the data type I would declare the
parameters (Menu bar  Query : Parameters ...), but that is optional in
Access for most queries.