Screen for optionable stocks

["Harold Harper" <harold@xxxx>]

Does anyone have a suggestion regarding how to screen for only stocks 
that are optionable? I use Yahoo day-end quotes and can't filter for 
ony optionable stocks. If I use, for example, as a buy condition:

MA(volume,20)>200000

might that help?

I guess what I'm asking is does anyone know a good rule of thumb 
regarding which variables (exchange, open, high, low, close, volume) 
might help in filtering for stocks that are optionable? Would it be 
fair to say, for example, that stocks priced greater than $10 with an 
average daily volume of x are generally optionable?

Thanks in advance.

Harold Harper
harold@xxxx