Calculate the rolling avg in a structure -- cell editor ?

Hello BW experts,

Here is an interesting scenario.

Rows: material, Structure: Net Sales(hide), total sales value(Net Sales restrict to doc type ZAA) , returns value (net sales restrict to doc type ZAB)

Columns: 0CalMonth restricted to 0CMONTH for rolling 24 months using value range and specify variable offsets -1 to -24.

Now I have to add a formula to the structure in the row 'Rate 12 Mo Average' = (Total Sales Value last 12 months ) / (Returns value last 12 months)

possible solution:

probably we should be in a position to use the Cell Editor. Could any one please explain how we can use it.

Wondering if there are any other possible alternative solutions to acheive the same funationality.

Any suggestions appreciated.

Thanks,

BWer