cell shows value because the formula is not been complete

ive got a setup where a you pick a item in cells A and in cells B it shows the price they then type the quantity of the item in cell C. And in Cell D i Have e.g. B1*C2 and its shows Value When no item selected but because of the way i need it to work is there some formatting etc that i can use to get it to put "£0" if no item is selected


thanks for your time

Josh