Hi Satyajeet,
Apart from posting area 0800 there is no way to update the return date field in SD request automatically.
There is no way through any event you can set the retrun date.
The only way is through an implicit enhancement is in the program, SAPLFKK_SEC under the form, CALCULATE_EXPIRE_DATE to set it with a desired date as per yuor requirement.
However, setting return date as 31.12.9999 and don't setting the return date at all is the same..Isn't it?
Thanks,
Amlan