[Swftools-common] scrollbar how to improve ?

[jean-michel.voicechat_fan]

i have a example for a scrollbar but i am not able to improve it when 
the edit zone grows
may be some one may help
it is an AS2 example
my FMS chat is on going i am working on video adds now
but it is difficult for me ...
i am more  PHP & javascript
<<attachment: jeanmichel_gens.vcf>>