Amortization in the security deposit

Hi ,

Bussiness requirment : To handle the Amortization in the security deposit ( FPSEC1 RM-CA Telecom project).

For Ex :

• Collecting 10,000 amount for two years from a customer as security deposit for using a product( DTH Installation at customer house).
  after completion of two years instead of refunding the amount to the customer the business requirment is to amortize the 10,000 full amount .
• Less than 1 year : If the customer wants to dissconect the DTH services & want security deposit refund .
  Bussiness requirment is to amortize the 50% of the security deposit amount .

Can you please suggest me the approach / Fqevents to handle the security deposit in RM-CA .

I tried using the event FKK_SAMPLE_0870 additinal checks before releasing the amount but this event is not triggering from FPSEC1

Regards
Rahul