Dear Sanjay Sontakke,
Yes, Its possiable to build a work flow approval mechanism at REFX contract Level.Based on your requirement you can use the REFX standard work flow mechanism with the help of your ABAPER.
Pls see the below screen shot where you can access the standard workflow option at contract screen.
Based on your requirement ( Price comparision / data chnage/ based on user status change / value based...etc anything based on your business requirement) you can have the workflow triggering point.Pls get in touch with your ABAPER to make use of the same.
Thanks,
Rao