Custom Scrollbars for dynamic text

Hi, I need help with making custom scroll buttons for a dynamic
text box, with external text. I am using this script at the moment
but i doesnt seem to be doing anything at all.

To scroll up:

on (press) {
scrollbarleft.scroll;
scrollbarleft.scroll -= 1;
}

Down:

on (press) {
scrollbarleft.scroll;
scrollbarleft.scroll += 1;
}

Can anyone help me?