How to fill a blank area with '*' chars ?

1. offizieller Beitrag

    Hi, my customer has some official docs wich requires no blank space at bottom of page. For example, a text it uses places only half page, but depending on merged text it can be larger or no, so left white space on page needs be fulfilled by '*' chars... like this:

    << - page begin - >>

    " bla bla bla bla bla bla bla"
    " bla bla bla bla bla"

    **********************
    **********************
    **********************
    << - page end - >>

    How can i calculate free space and how to fulfill it ?

    thanks