Sumproduct using an array create on the go...

I'm trying to use the sumproduct function where one of the arrays are created on.

The data in one column is like:
4.40/4.75
3.25/3.25
5.60/5.70
2.56/2.56
6.04/6.04
11.05/12.12
8.00/8.92

and in the other column
1000
525
390
450
2500
150
660

Sometimes I want the portion left from the "/" to be used in the sumproduct and sometimes I want the portion right from the "/" to be used.

So the Sumproduct result for 1st case will be 31479.75 & for the 2nd case will be 32636.45.

I know splitting the columns data in two using "/" as delimeter will do the job but I do not want to add any extra columns in sheet as it has a format fixed.

Can anyone help? I'm using excel 2010

Thanks John