how to decrease height of header at runtime

I have a Report Viewer with Header.visible = true.

on the Header, I have some control: textbox, label, PageNumber,... there is have 4 rows

I want to show all control on header in first page and hide on next page and PageNumber show all pages. I use Expression to do this, but Height of header not decrease when controls which is hide (from 4 rows to 1 row, 1 row for show PageNumber) => How can I decrease header when control hide on next pages ? 

thanks for any solution.