Hi Anithosh,
First thing is that, you are sure you need to update with CRM_EVENTS only right. Why can't you use some badi?.
If you have to use CRMV_EVENTS, following steps are to be done.
1) Create two FMs Z_FM1 and Z_FM2.
2) Trigger an event in Save with CRMV_EVENT by calling Z_FM1.
3) Make the Z_FM2 as an update FM.
4) Write your whole code in Z_FM2.
5) Call Z_FM2 inside Z_FM1 like below.
CALL Z_FM2 IN UPDATE TASK.
This will work.
Thanks,
Faisal