How to select a base member based on PARENTH1 in script logic ?

HI ,

My requirement is simple of allocation

consider a simple Hier as below

The value will be posted to the "America_default" and that value needs to be alloc for the base members of Parent "America".

This had to be dynamic.

Is there any way we can access the Surrogate(America_default) ,if the user selects the Top node(America) when execution. ??

I know a work around by adding a property and entering the Surrogate Id at the parent level and then access it via SELECT

but we have a huge Hier structure and maintaining this will be a nightmare

does anyone has a better solution ?

Thanks in advance

Aamer