Changing name of Jasper report dinamicaly

Hi,

I have got a problem, when two people run same jasper report (notaspese.jrxml)  simultaneosly from their browser,

the files created in the server  have the same name "notaspese1297853083.pdf", and the last overwrite the  first!

The numeric part of the report name rappresents the numeric  format of Unix date time rappresentation,

then two reports made in the  same instant, have the same name!!!

Is it possible to change dinamicaly the litteral part of the report name?!

in detail, if my report name is notaspese.jrxml, I would like to have:

notaspese_USER_1_1297853083.pdf and notaspese_USER_2_1297853083.pdf

where the part USER_1 and USER_2 depends by the user who run the report?

thanks in advance,

Federico