Lua onThrow

[GOD Fito]

How can i do it to return false if i throw an item from my backpack to another backpack which is in the floor?

I did this but obviously it return false even if i throw items beetwens my backpacks

function onThrow(cid, item, fromPosition, toPosition)
if (isInArray....item) and fromPosition.x == CONTAINER_POSITION and toPosition.x == CONTAINER_POSITION then return false end
return true
end