Creating a Power Slider for an Archery Game

I am wanting the power slider to scroll up and down the power bar continuously until the user left clicks.

Then i am wanting the Y position of the power slider to be transformed into power. So the higher up the power bar the more power.

I have created the power bar and the slider sprite but am unsure of how to set the events up.

Thanks, Rabbit

QuickArchery.capx

Will have to check this out when I get home.

But here's a question based off my memory of playing Thief2 and Wii Sports Resort years back:

Why not make it so that when you hold down the mouse left it begins pulling the bow string and arrow back (and stretches the power slider) until the player releases the mouse button. Then the arrow flies off toward its target??