How to prevent maintenance of an editable key figure at any higher level other than it's base planning level?

Hi All,

We have a scenario here where we would like to prevent maintenance of an editable key figure at any level other than it's base planning level?

Example - We have a key figure DEMANDFORECASTQTY at base planning level as PERPRODCUST and it's editable in the current and future, so we can edit this key figure only at product id and cust id level but not at any other higher aggregate level.

Please let me know if this can be done, if yes please provide how we can do it?