In report design view, click on View | Sorting and Grouping (I'm making the
assumption that you are using Access 2003 or earlier. If you are using Access
2007, the logic will be the same, but you'll have to find the corresponding
steps using the ribbon). Add your OrderID field to the Sorting and Grouping
dialog, with Group Header = Yes, Group Footer = No, Group On = Each Value,
Group Interval = 1 and Keep Together = Whole Group.

Expand the Report Footer section, if it has a height of zero. Add a text box
with the following calculated expression:

   =Count([OrderID])

Where OrderID is the name of the field. Make the appropriate substitution if
your field is named something else, such as [Order ID]. Make sure that the
name of this text box in not the same as the name of the any fields involved
in the expression.

Tom Wickerath
Microsoft Access MVP
http://www.accessmvp.com/TWickerath/
http://www.access.qbuilt.com/html/expert_contributors.html
__________________________________________

Duane's solution should work with your daily report, but if you are first
grouping the weekly report by days then the same OrderID could appear in more
than one group header if picked and loaded on separate days as this would be
the second group level, so it would again be counted twice.

A solution would be to count the distinct OrderID values in code in the
report's module.  First you'd declare two module level variables, one to hold
a value list of the distinct OrderIDs, one to hold the count.  In the detail
section's Print event procedure the OrderID would be added to the value list
and the count incremented each time a new OrderID is encountered.  Finally
the value of the count would be assigned to an unbound text box in the report
footer.  So the report's module would look something like this:

Option Compare Database
Option Explicit

Dim strIDList As String
Dim intIDCount As Integer

Private Sub Detail_Print(Cancel As Integer, PrintCount As Integer)

   If PrintCount = 1 Then
       If InStr(strIDList, "~" & Me.OrderID) = 0 Then
           strIDList = strIDList & "~" & Me.OrderID
           intIDCount = intIDCount + 1
       End If
   End If
   
End Sub

Private Sub ReportFooter_Print(Cancel As Integer, PrintCount As Integer)

   Me.txtOrderCount = intIDCount
   
End Sub

Note that I've used the tilde character as the delimiter for the value list
rather than the more usual comma, colon or semi-colon.  This is just in case
you are using a structured OrderID (or equivalent) which might contain one of
those characters.  I'm assuming it won't contain a tilde!  If it’s a simple
number such as an autonumber it will still work of course.

Ken Sheridan
Stafford, England