Is there a tax calculator for self employed people?

Hi
is anyone aware of an Irish tax calculator for self employed people?All the calculators linked on A.A.M. or that I've found on Google are P.A.Y.E. based.
I DO have an accountant, but I would like to be able to figure out my liability myself too.
Thanks in advance

Nicola

The ROS Offline software available from ros.ie?

Thanks ubiquitous, this looks v promising!
I'll give it a go after work

N