I am serving in UN. UN pays me in US Dollars. I transfer some portion of that in my Foreign Currency Account in a Bank at my country. The Bank said during transaction they will not provide me US Dollars but the local currency whatever is the rate persists at that perticular time. The Dollars are remaining in that account for some period of time. So, will it be Haram/Halal to exchange it whenever the rate increases?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is permissible to delay the exchange of the amount till the rate rises. However, we draw your attention that depositing money in a bank which deals with Ribaa (usury and/or interest) is not allowed except if there is a necessity. If one is forced to deposit in such a bank, then he should deposit in a current account and not a saving account and should withdraw his money as soon as the necessity ends.