Very basic method. Make your custom slider. Put the following script on it (I am doing this off top of my head and haven't used director for about 6 months, you may need to work it a bit)
property spritenum
on exitframe me
' this checks they are movieing the slider
if the mousedown = true and the mousemember = spritenum then
'this bit limits where the slider can be put
if the mouseV < 100 and the mouseV > 0 then
sprite(spritenum).locv = the mousev
end if
' get the % of the max distance it can move
percMoved = sprite(spritenum).locv / 100
' now to make the thing scroll
' I dont know how to find out the max scroll so this is hard coded. Try to work it out, hard coded is evil
member(textmember).scrolltop = 200 * percMoved
end if
end
Now, this should (its untested and ugly) do what you need. There are other ways to control the movement of the slider, and probably better places to put the code that scrolls the text, eg lingo dictionary puts their scroll code in prepareframe.