counting records in parent table

[bilalo]

I have a parent table named order and a child table suborder where each order contains multiple suborders
I created a report that shows all orders and suborders grouped by OrderID.
I need to show the total number of orders., I used the function count(OrderID) in the report header but its showing me the total number of records in the report query which is count(SubOrderID) instead of count(OrderID).
What am I doing wrong?

[June7]

Try DCount() instead.

=DCount("*", "Order", "same filter criteria as applied to the report")

[bilalo]

Try DCount() instead.

=DCount("*", "Order", "same filter criteria as applied to the report")

The problem is that the orders are also grouped by date, so I need a dcount(orderno) for each month.
I tried a dcount with filter on month(orderdate) but when the result is blank it is showing errors.
I was thinking to use something similar to dcount(disctinct orderno) without applying any filter, in this case I do not have any repetition of suborders, is there something that works like this?
Finally, I am wondering, is it true that ms access do not have a simple function like count(orderno) to count parent records directly from the report query?

[June7]

Correct, Count() will count records of the query that is the report RecordSource. DCount() must reference table or query object and cannot modify with "DISTINCT".

What do you mean by 'grouped by date'? A group section on year/month? You originally stated you wanted count of all orders in report header, that would not consider year/month. A DCount in group section could return count by year/month.

=DCount("*", "Order", "Format([OrderDate], 'yyyymm')=" & Format([OrderDate], "yyyymm"))

Why would result be blank and cause errors?

If you want to provide db for analysis, follow instructions at bottom of my post.