Customer Orders, shipments and invoices in one report

It should show Current Month Bookings, Current Month Shipments, Current Month Invoices against the Customer.
I created a new report by taking Customer table as source and written the code to show current month as
monthStart := CALCDATE('<-CM>',TODAY);
monthEnd:= CALCDATE('<CM>',TODAY);
SalesHeaderRec.SETRANGE("Order Date",monthStartDt,monthEnd);
SalesLineRec.SETRANGE("Shipment Date",monthStartDt,monthEnd);
SalesLineRec.SETRANGE("Posting Date",monthStartDt,monthEnd);
it was showing empty on it.
Can any one please suggest me regarding this issue.
Thanks in Advance.