Running total calculation from blank celled records

[loungeroom]

I'm trying to create a formula out of this:

If an item has not been sold then the sold column will be blank.

If it is blank then I want to take the figure out of the price paid cell and put the total of all unsold items into one cell to generate a running total of stock.

I can do this with the formula =IF(CELL("type",C13)="b",(B13),"Other") but this only generates the total from one record and not all records.

An example of the sheet is here:
http://i1166.photobucket.com/albums/q617/lj_trading/example.jpg

Thanks all

 

[Vidar]

=SUMPRODUCT(B7:B31,(--(C7:C31="")))

Expand the ranges to your needs.

Vidar