Short range Left/Middle/Right. IR?

I'm quite new to arduino but I have a project in mind.

I need a senor that can detect very short range left/middle/right position of a finger or similar object. It should be able to detect left/right movement of a finger that is hovering back/forth within a few millimeters of the sensor.

I'm thinking I can achieve this with a sensor like this: http://imall.iteadstudio.com/im120712017.html or maybe two of them?

Can someone please point me in the right direction?

Thanks,
Thomas

Yes that sort of sensor is good for a few mm. However it is susceptible to interference by ambient light especially sunlight

Grumpy_Mike:
Yes that sort of sensor is good for a few mm. However it is susceptible to interference by ambient light especially sunlight

Thanks. Light won't be an issue - it will be used in darkness.