Share application money

Hello Friends,

We have received share application money in US$.but we have not convereted that money into shares.

Now we want to revert back that application money with interest.

do I need to calculate interest on US$ or indian rupees.

Suppose we have received US$ 1000 and we have converted that amount into 50000/- 

do we need to calculate int on US$1000 or rs.50,000/-

Please clarify.