Need help receiving btc to local (offline wallet)

[papaminer]

Let's say..

I sell 99999999 items online....

I will provide my wallet address and users send btc to that address...

How can I determine... which is which without a label?

For example:
person1 buys an iphone4 for 1BTC and sends the btc to my 1wallet address

person2 buys and iphone5 for 5BTC and sends the btc to my 1wallet address...

How can I determine which person paid/sent money?

[CIYAM]

The best way would be to create a different address for each and every transaction - note that the re-use of addresses is not advised.

[papaminer]

is there any API that does that?

Like... how do bitmit.net handles thousands of sales...

[CIYAM]

As you are wanting to do this with an "offline wallet" you might be best using a deterministic wallet (not yet part of the Satoshi client) otherwise you would need to pre-generate a bunch of key pairs (using say vanitygen) and transport the public ones across to your online computer.

[papaminer]

Okay...

How about that mtgox button? from their merchant tool?

I just checked and it says it is free..

but I am not sure about withdrawal from mtgox into my offline wallet... (is it still free?)