IF ISERROR and VLOOKUPs

=IF(ISERROR(VLOOKUP(E6,CostTable,2,FALSE)*E6),0,VLOOKUP(E6,CostTable,2,FALSE)*E6)

use the above to solve your Excel 2003 Vlookup error requirements, this enables SUM calcs to still give you an answer  and replaces error cells with zeros.

J