How to know current page number

I created a few pages. How can i know index number of current page?

e.g.

Page custom PageOptions PageOptionsLeave ;order number is 0
Page custom PageExOpt PageExOptLeave ;order number is 1
....
Page custom PageNCreate PageNLeave ;order number is N

Nsis creates this pages in this order. First page is PageOptions then page PageExOpt ...
I want to know order number when i stand on each page. Thanks

Simply do this:
!define PageOptionsNumber 0
Page custom PageOptions PageOptionsLeave ;order number is 0
!define PageOptNumber 1
Page custom PageExOpt PageExOptLeave ;order number is 1
!define PageNCreateNumber 2

And then refer to it by ${PageNCreateNumber}.