I have this formula that subtracts one cell from another and then adds that
to a running total.

=(C672-D671)+(C673-D672)+(C674-D673)+(C675-D674)+(C676-D675)+(C677-D676)+(C678-D677)+(D678-C678)


My problem is this; on occasion there will be the need to have some cell
pairs blank or they'll contain "N/A" in them. When this happens I get a Value
error. How can I correct this?


Thanks in Advance,
Rob