can i programme a cut key for my 2000 citroen berlingo or is it a main agent job

Chances are you will need a Citroen dealer to do it for you.

Defiantly Citroen dealer key has to be coded to vech ECU.

l am sorry to say but they are right, the only people that can reprograme the keys are citroen themselves.
l hope you have still got the paperwork that came with the car, because inside it is the key code & other info that they need, without this it is going to be VERY expensive.
Sorry to be the burden of bad news.

Yes it needs to goto a main dealer to be coded . The transponder number is required which is a 4 digit hexidecimal code which if you do not have can be applied for by a citroen garage which there is a charge which is simply passed on to you because the dealer will also get charged for the service.