I want an item to take damage everytime its getting used for crafting i have tried this:

http://www.minecraftforge.net/forum/index.php/topic,2137.0.html

topic but it doesnt seem to work eclipse gives an error if someone can explain it please

If it doesn't work, you're doing it wrong. Show me the error.

It works but when the damage reaches 0 it doesnt disapear

Try something like this (it's the same method from vroominator with additional 2 lines):

 

    public void onCrafting(EntityPlayer player, ItemStack item, IInventory inv) 
    {
        for(int i=0; i < inv.getSizeInventory(); i++)
        {        	
            if(inv.getStackInSlot(i) != null)
            {
                ItemStack j = inv.getStackInSlot(i);
                if(j.getItem() != null && j.getItem() == Your Item)
                {
                    ItemStack k = new ItemStack(Your Item, 2, (j.getItemDamage() + 1));
                    // these two lines are added by me:
                    if(k.getItemDamage() >= k.getMaxDamage())
                        k = null;
                    inv.setInventorySlotContents(i, k);
                }  
            }
        }
    }

it worked thanks