how to display page number starting from given number

hi all,

 Till now i'm using page number in header and footer so that the page number starts from 1

="Page " & Globals!PageNumber 

but now i need page number starting from what number i needed

i have one parameter in which values come from drop down as 1,2,3,4,5..etc

now if select parameter value as 1 my page number should start from 1..if i select 2 it should start from 2...etc

how can i acheive this..

pls help

thanx in advance..

lucky