Specific performance Case

In the year 1981 my father had entered a sale agreement for a property for 15K, out of whic he had paid 5k as advance. Later the seller did not come and fullfill his part of the duty - registration. Hence a case was filed and the decree was passed in 1998 that the property needs to get registered by paying balance 10k to seller/court. But parallelly there were RA appeals on the same property claiming individual share which were later dismissed. Later in year 2006 we filed a request for court commission to execute the final sale. But seller filed a IA saying that we have not done our duty by not paying 10k after decree in 1998 and he will be under huge loss as the property value has increased. For this the court passed a decree dismissing the decree of 1998. We made a appeal in High court also, but there also our appeal got dismissed. Meanwhile the seller has sold the property to someone in 2011. Recently we got our appeal dismissed in high court. Please suggest how to proceed with this situation