Hi Vishu,
You can schedule Above program which is shared by Nanda in background as per needs(weekly or monthly).
Or
You can create a process chain and use ABAP Program process type.
in that you can enter program RSIMPCURR along with variant.
You can schedule your chain as you need in background.
for more information, please search on google and find useful pdf.
Use google search word as "Step by Step Method for Automated Transfer of Global Settings and Exchange Rates ".
Thanks
Raman