transaction and concurrency control

[manish237]

hi

I m developing a code repository.
My query is regarding transaction and concurrency control . i m using sql server 2k.

I want to add following functionality:
Whwnever a user tries to add a code i would like to check if anybody else has uploaded the same code during the current user's transaction. If smone else has uploaded same code i want to give a message to current user that the code is uploaded.

Please tell me how should i go about this . A small piece of code would be appreciated.

Thanks