Clean iPod Click wheel

Exactly what the title says! lol
here is what I have,


(sorry for the poor quality, i just took a quicky with my iSight)

anyway, I think it is a grease stain from my finger, because that is where my finger sits most of the time. I have tried rubbing it with water, but it still remains,

any idea's how to get it off?


Thanks,

 

No One??
Cant imagine im the only one who needs to clean their click wheel!