Runtime Error 2585 (this action can't be carried out while processing a form or report event)

I have a command button (cmdPurchaseOrderPrint) on my form (Orders) that opens a print dialog box for a report.  When I click 'ok' to print the form I see Error # 2585, This action can't be carried out while processing a form or report event.  Debugging reveals the offending statement is RunCommand acCmdPrint.    

Here's the code behind the click event of the command button:
DoCmd.OpenReport "PurchaseOrder", acViewPreview

And here's the code behind the on open event of the report:

Private Sub Report_Open(Cancel As Integer)

On Error GoTo Error_Handling:

Dim cn As ADODB.Connection
Set cn = CurrentProject.Connection

Dim rstOrders As New ADODB.Recordset
Dim strSQL As String

If CurrentProject.AllForms("Orders").IsLoaded = False Then
    Dim OrderNum As String

Get_Input:
    OrderNum = InputBox("Enter Order #")
    If OrderNum <> "" Then
        strSQL = "SELECT Order_Num FROM tblOrders WHERE Order_Num = '" & OrderNum & "' "
        rstOrders.Open (strSQL), cn, adOpenForwardOnly, adLockReadOnly
        If rstOrders.EOF = True Then
            MsgBox "Order #" & OrderNum & " Not Found!", vbCritical
            rstOrders.Close
            GoTo Get_Input
        Else
            strSQL = "SELECT * FROM tblOrders WHERE Order_Num = '" & OrderNum & "' "
            Me.RecordSource = strSQL
        End If
    Else
        End
        DoCmd.Close
    End If

Else
    strSQL = "SELECT * FROM tblOrders WHERE Order_Num = " & Forms!Orders!Order_Num
    Me.RecordSource = strSQL
    RunCommand acCmdPrint    
End If

Exit Sub

Error_Handling:
If Err.Number = 2501 Then  'user canceled print dialog box
    End  
Else
    MsgBox Err.Number
    MsgBox Err.Description
End If

End Sub

Any idea what I'm doing wrong?

Thanks in advance.