help with sample size calculation

[sky1]

I have group proportions of three groups, and I want to calcualte the sample size of each group (assuming equal sample size in each group, power is 0.8, alpha is 0.05).

This type of calculation is easy to do when there are only two groups. I can use proc power; twosamplefreq. Does anyone know how to do it with three groups? Thanks

[AncaTilea]

Apparently you could do it as they did it here:

http://www2.sas.com/proceedings/forum2008/368-2008.pdf

see bottom of page 1.