Restricting selecting in COGI

Hi,

I have a scenario, in which I want to allow the end user to select only 500 Line Items in COGI

i.e. restrict No. of line items to be processed in COGI

How can i do that !? As i guess there are no User Exits nor any Screen Enhancements.

I was thinking of Transacation Variant, but i doubt if i can apply any logic there.

Please guide.

Thanks in advance,

Harris