I have a form with 3 combo boxes on it to select items to filter a query on.  I am showing the data from the filtered query in a form.  I would like the filter to use the selection from any single combo-box or or combination of 2 combo-boxes.  Here is the code in the query I am using.  It works fine when doing any single combo-box but when adding the last or statement for the 2 combo-boxes it will not return data.  If i have only the 2 combo-boxes and none of the single filters it works.

SELECT TBL_Purchase_Order1.PO_Num, TBL_Purchase_Req1.PR_Num, TBL_Purchase_Req1.Requestor, TBL_Purchase_Req1.Vendor, TBL_Purchase_Req1.PR_Description, TBL_Purchase_Req1.PR_Date, TBL_Purchase_Req1.Approver, TBL_Purchase_Req1.Send_Approval, Sum(TBL_PR_Lines1.Cost) AS [PO Total]
FROM (TBL_Purchase_Req1 LEFT JOIN TBL_Purchase_Order1 ON TBL_Purchase_Req1.PR_Num = TBL_Purchase_Order1.Purchase_Req_Num) INNER JOIN TBL_PR_Lines1 ON TBL_Purchase_Req1.PR_Num = TBL_PR_Lines1.Purchase_Req_Num
GROUP BY TBL_Purchase_Order1.PO_Num, TBL_Purchase_Req1.PR_Num, TBL_Purchase_Req1.Requestor, TBL_Purchase_Req1.Vendor, TBL_Purchase_Req1.PR_Description, TBL_Purchase_Req1.PR_Date, TBL_Purchase_Req1.Approver, TBL_Purchase_Req1.Send_Approval
HAVING (((TBL_Purchase_Req1.PR_Num)=[Forms]![FRM_Reports_Queries]![Combo_PRnum_Filter])) OR (((TBL_Purchase_Req1.Requestor)=[Forms]![FRM_Reports_Queries]![Combo_Requester_Filter])) OR (((TBL_Purchase_Req1.Vendor)=[Forms]![FRM_Reports_Queries]![Combo_Vendor_Filter])) OR (((TBL_Purchase_Req1.Requestor)=[Forms]![FRM_Reports_Queries]![Combo_Requester_Filter]) AND ((TBL_Purchase_Req1.Vendor)=[Forms]![FRM_Reports_Queries]![Combo_Vendor_Filter]));