Flv adjustable speed

Hi,
I have question, is it possible changing speed .flv files in flash (actionscript)?
ideal: combo box, with:
‘speed 100%’
‘speed 50%’
‘speed 25%’
and then click on play button.

I know, that I can do above by changing fps in convert process .AVI to .FLV and then make three files. I will be have about 40 avi files, its mean 120flv. That’s why I have question if I can regulate speed by different method.

Thanks Jan