Someone please help ! Have looked everywhere.

I have created a worksheet where the user enters an item and a price and the
worksheet calcs the unit price.  Like this:

A                        B                  C                    D
Item                   Price              Units              Price per Unit
Cheese               $ 10.00          2                    =b1/c1      so $
5.00 is answered

That's fine as long as there is any entry, with no entry say onthe 2nd line
it looks like this

A                        B                  C                    D
Item                   Price              Units              Price per Unit
Cheese               $ 10.00          2                    =b1/c1      so $
5.00 is answered
blank                  blank             blank               # DIV/0#

It is this error (#DIV/0!) thats my issue.  The answer (when an entry is
made) the $ 5.00 is posted into aother worksheet...but the #DIV errors are
causing subsequent #DIV errors when I try to say...add the colum or do
anything else with that group of data.

I need the user to be able to enter multiple data, but I need to be able to
make the calcs without comming up with the #DIV when the user leaves the line
blank.

Please Help!