You’re getting that “left side blah blah blah” error because you can’t change a variable on the left side of the equals sign.
Try changing:
on (press) {
angelasecondtry.scroll-1=1;
}
To:
on (press) {
angelasecondtry.scroll += 1;
}
OR:
on (press) {
angelasecondtry.scroll -= 1;
}
The above is/are the shorthand version of:
on (press) {
angelasecondtry.scroll = angelasecondtry.scroll + 1;
}
You could even do:
on (press) {
angelasecondtry.scroll++;
}
OR:
on (press) {
angelasecondtry.scroll--;
}
That should work for ya (assuming everything else is in order or course). Just remember – you can not ever (in Flash) assign/change any properties of a variable on the left side of the equals sign. 
