Drafting: Page number in title block

Good day,

While drafting a title block in NX 12, what is the way to set a cell to be populated automatically with the sheet number? I ask this because i´m working with a file that has several sheets. If i edit the title block with the corresponding sheet number (sheet 4 of 25 for example), it is updated for all the sheets.

I´m sure there´s a function for this, but i ignore it.

Thanks.