prevent user from use it's own coupon [#2631502]

Hi, first of all, sorry for my english.

i have a complex site with the next funcionality:

every user have it's own coupon code, which one can be shared to other users. If any other user use this coupon, the owner recibes some userpoints. no problems.

but, i need to prevent user from use it's own coupon.

i'l explain again.
hook_user_insert
custom function executed, http://c2n.me/3rsNLV0
now, every user have a code with reference to this user
i need to prevent the usage of this coupon for this user (this coupon is only for share)

i have tried to enable commerce coupon user module, but i can't figure, how to do this condition.