custompages text ontop of window in white space

How do i put text in the white space at the top of cutom pages, right now it is is just blank and I can only put text on the title bar, and inside the grey window by using a label

Before you do a MUI_INSTALLOPTIONS_INITDIALOG
or a MUI_INSTALLOPTIONS_DISPLAY enter this line

!insertmacro MUI_HEADER_TEXT "The title" "The subtitle"

thank you