[Automatic Blinds]

Hi,
I am looking to build a devise that will open my vertical blinds in the morning and then close these in the evening when light fades, automatically using LDR. Therefore, I want to power a geared dc motor so that it alternates its controls to rotate clockwise and counter-clockwise. Also I need to control the speed of the motor. Could someone please help me with a circuitry to do this.

[Reverse polarity]

Access to 12 V -  Yes I am using the same battery pack as a power source, which was part of the drill, which is rechargeable.
The drill also has a manual button that reverses the motion, ie used to screw/unscrew, but this is a manual button. Can this be controlled with any sort of an electrical gadget which will basically do the work of manually pushing this button. Will a contactor relay help at all?

[Reverse polarity]

How do I make a motor to alternatively reverse its action everytime power is switched on  i.e. if clockwise on first switch, anticlockwise on second switch and so on. The motor (taken out of a chordless hammer drill) runs on a 12V dc.