invoiced quantity prevent item cost to be 0 proplem

I have invoiced quantity to specified item and i need to revaluation to this item cost to 0 what i do because revaluation not

accept invoiced and i have item all quantity and cost is 0 but only invoiced quantity remaining NOT accept revaluation and i

don’t know what i do to make it 0 .I want to do this because some users enter wrong cost and this require to modify all

and it will affect in g/l

if possible what i do or give me solution