Reports 2.5 and Page Numbers!!!

 I have this problem:

 I need to show a field label depending on the page number like this... for pages from 1 to LAST_PAGE-1 I show 'Sub Total' and for the Last Page I'd like to show 'Total' instead of 'subtotal'.

 I've tried to use two fields containing &Physical Page and &Total Physical Pages and use them on a Format Trigger, but I cannot reference their values...

 So, I will appreciate very much any suggestion...

 Thanks...

                                             Manuel Jerez..