Creating same rebate agreements

Hi Everyone

Can someone tell me please why its allowed to create same rebate agreementu2019s with the same Customer , validity dates and material

And which one of them is updating the invoice?

second thing is how can I avoid that from happening ? is there a note about it or only customization needed?

Regards

Zachi.

Edited by: zachile on Feb 7, 2012 4:11 PM