Converting a column into an expression

Hello All,

There is a column of numeric data I would like converted into an expression. This expression would then be nested into a secondary expression.

This column has payment data and  the "do not summarize" option selected.  In the example below, the desired result is to have the payments listed so :

Customers  Payments

Allen           $50

Steve           $60

Allen           $10

Would become:

Customers  Payments

Steve           $60

Allen           $50

Allen           $10

The problem is when writting  a measure, the column must have an aggregate before it, such as SUMX. This would combine Allen with $60, where I need the split of each customer and their payment. What would be the best way to convert the payment column into a measure and not consolidate the customer data? 

Thanks