Hi Raja,
You can follow 2 approach:
1. update historic values for all entity for that gls - Here while doing currency conversion, system will first check the entity and FX TYPE property, and will consider historic values only for those entity where "AS_IS" is maintained and for other entities, system will look at the local currency and will convert the same at closing rate
2. update historic values only for that entity which will be converted at historic rate system will only look at the historic values for the entity for which it is maintained and for the rest of entity, system will look at local currency.
Regards,
Rahul