Hi Snehal,
Have you tried searching our GitHub communities for an existing app? There might be something out there already. Use the links below :
Rally Community · GitHub
Rally Software Tools · GitHub
Here is one example I found doing a quick search in the community area on Enhanced Velocity Chart.
If you do not find anything that fits your needs from the above links, you can reach out to your account representative to request assistance from the CA Agile Central Technical Services team. This team provides custom application services to customers for a fee.
Hope that helps,
Sean Davis