I WOULD START WITH SOME OF THE URINE CLEANER FOR PETS TO GET RID OF THE SCENT & THEN SPRAY THE AREA WITH BITTER APPLE (CAREFUL ON WOOD FURNITURE AS IT COULD STAIN). IS THE DOG NEUTURED AS SOMETIMES THIS HELPS WITH TERRITORIAL MARKING? SOUNDS LIKE A DOMINANCE ISSUE THAT MAY REQUIRE SOME SPECIALIZED TRAINING. GOOD LUCK!