Lookup/Match and Sum Multiple Values

[SAsplin]

Hi,

In the example I have included columns A and B contain old material numbers. Column C contains a master list of current and old numbers(ie. all numbers in columns A and B 'should' appear in column C). Column E is a list of values.

What I would like is a formula that -

a). If columns A and B are blank returns the value (in column E) of the material in column C
b). If there is a value in column A bring back the adjacent value in column E twice (once for the old material (col A) and once for the new material (col C)
c). If there is a value in column A AND column B bring back the adjacent value in column E three times (as above).

There would never be a value in column B without a value in column A.

I tried the unweildy:

=IF(AND(A5<1,B5<1),E5,IF(B5>0,INDEX($E$2:$E$6,MATCH(A5,$C$2:$C$6,0)+INDEX($E$2:$E$6,MATCH(B5,$C$2:$C$6,0)))+E5,IF(A5>0,INDEX($E$2:$E$6,MATCH(A5,$C$2:$C$6,0)+E5))))

This seemed to work until I had to enter a new 'old material' in column A and the formula returned #REF! (see example).

Any help on amending my formula or suggesting a better alternative would be most welcome.

Thanks,

Steve