How to get target file name and buffer the incoming messages?

Hi Experts

I have one scenarion like

I wanted to find whether is there any file existing in target folder. If it exists I dont want to overwrite it but I have to buffer the incoming messages in some queue or something like that. And when ever the request comes next time I have to send the data buffered in queue first.

I dont want to add any time stamp for target file to avoide duplication.

Can we do this using XI. If yes please suggest me how to achive this.

Regards

Sowmya