Problem with the same content of an context in different sessions

So here is the problem.

I`ve got my web dynpro running on NetWeaver2004. In my application I`ve got an input field and a button. To this input field is bind context variable type string. Then i do just trim on this context, and call rfc function with this context as import parameter. The rfc sends me back correct export parameters. So this is ok. Then I write on the screen the import parameter and all export parameters.

But when I run two session of this application. There i get a problem. From the first session I call the rfc with for example parameter 123 all the things run ok. Then I call rfc function from the second web dynpro with for example parameter 456. This runs ok too. But when I call from first session onesmore rfc with parameter 123. It will get back from R3 data for 456 and the context import parameter is 456!!! But i put in inputfield 123 and this parameter i`m using only in my program as context variable. So the question is why the second session changed my context in the first session. And what i must do to avoid this happen.

Thanks for help