Flash animation help

I am a complete novice when coming to using Flash but I am looking to create an animation similar to the line into text animation at:

http://www.louisebradley.co.uk/fl/

where instead of running from the top of the screen I want the line to effectively stretch across my homepage horizontally.

I have created an animated gif that does the job but it takes a long time to stretch across 974 pixels in width, and if the frames are reduced it takes away any smoothing effect. I did this in photoshop by simply creating 20 or so frames, each increasing the size of the line by 60 pixels until 开发者_如何转开发the full page is covered.

Would I be better off creating the effect in Flash? And if so, where on earth do I start!! Would tweening do this, and how I would I implement it?

Thanks in advance for any help!

I am assuming you are talking about the line to the left of the main navigation? If this is the case, this is being done using a mask that is tweened. You can simply draw out the shape you want "wiped" across the screen and than on the layer above it, draw a box over the shape to be animated. Right click the layer the box is on and select "mask". You can now tween the mask to move from right to left over the shape you drew and it will appear to wipe over. Just remember, whatever the mask is currently over, is what will show through from the layer that is masked. Think of the mask as a window. This can be completely done without actionscript and only using the timeline.