Allocations - Divide by Basis

I have the following Allocations step in rel 9.2 that is not performing as expected.  I want to select a Pool record and divide the amount by the amount in the selected Basis record.  However allocations is summing all Basis records to determine the divisor.

For example, for this Pool data:

Business Unit       Account       Amount

10000                   60000          200

10001                   70000          300

10002                   80000          500

and this Basis data:

10000                   60000          200

10001                   70000          600

10002                   80000         1000

I want it to calculate 200/200 and generate a Target record using account 60000, then

                 calculate 300/600 and generate a Target record using account 70000, then

                 calculate 500/1000 and generate a Target record using account 80000.

However the step is summing all Basis records and using that sum as the divisor, so it is: