subtraction with different way

hi experts
I have two sheets contains items should subtrct between two sheets and show the whole data in another sheet . usaully the items contain empty cells below th item . in this case in first sheet for ITEM AA-1000 start from the first cell contain this item and end to last empty cell before start a new item and so on for all the items with there is exception somtimes there is no empty cell under the item as in TT-100 . about the second sheet there are many items in COL B .in this case should subtract the first sheet based on COL B,C,D for each item in COLA from the second sheet based on COL E,F,G for each item in COL B . it should subtract for each ITEM in COL ITEM .
the third sheet is expected result should be after fill for first and second sheet then should show the changes
with considering if there are items in first sheet but not existed in second sheet then should also copy to third sheet below the item is relating of it with show mark "-" in col B,C as show in third sheet

finally if there is not clear just inform me to add more details
thanks in advance