AS3 videoplayer

I’m building a flash video player in AS3, but having troubles with the progress scrubber.
this is my code that i think i’m having troubles with:
controller.playbox.x = (nsStream.time/objInfo.duration) * (controller.f_middle.width)

playbox is the scrubber, f_middle is the progress bar.

The problem is that the scrubber always starts in the most left of the symbol it is with, which is not where I want it to be. The scrubber should start where the original place is.