Hi Kamal,
This can be done by using Premature Settlement Option in FTR_EDIT.
1. You'll need to enter the no. of dollars you are settling before maturity i.e in your case 20000. So two transactions will be created here i.e 103 and 105. Transaction 105 has to be posted immediately while 103 will be posted on maturity.
2. Also, the original transaction will need to be posted on maturity.
3. The net effect of the original transaction and 103 will be 80000 dollars.
4. You can follow these steps as many times as you want as long as there is a balance existing in the contract.
Please let me know if this is clear.
Regards,
Rohit