Problem with TotalPages when printing more than one report

Hi everyone,

I am having a problem with page numbers in NAV 2013 reports.
I am using a textbox with the following expression:

It works just fine when I print one report at a time, but when I print many reports together, it gives me something like:
Page 1/20, Page 2/20, Page 3/20, etc...as if it was only one document...
How can I fix that???

Thanks in advance