Scrollbar arrows

so im modifying kirupa’s tutorial, loading external text files

and i took away the scrollbar component, in favor of graphical arrow buttons

im using this code from another tutorial on sending a form with php to make the text scroll


and the other button has scroll–;

the problem im having, is that you have to push the arrow button a million times to get to the bottom of the document,

how can i make it so when you press down the button, it continues to scroll until you release?

some sort of if…else loop?