[Forums] Combining data input with existing record data

In our app we need to allocate a given amount of value to a number of different investors.  The allocation is relatively simple as each investor gets a proportion of the amount to allocate equal to their proportion of the total amount invested.

We are looking at having a web page that performs this calculation and create the relevant records once calculated.  The web page would look like the table below but combines 3 different things.

1. Pulls information (name and SUM for a particular attribute) from a specific Data Entity (this info is shaded in light green in the table below)
2. The amount to be allocated is input in the table (this is shaded in light orange in the table below)
3. Calculation based on the input and data pulled out (this is shaded in light yellow in the table below)

The number of items listed (ie rows) will vary depending on what is queried. 

Interested to get thoughts on the best way to do this.  It seems like a table or editable table where most of the data is locked down but can't seem to get it to make the relevant calculations and let the first line of the 3rd column be an input