another tax question

Hailing all accountants and those that do their own tax.

I will be completing my first tax return for trading shares, and use commsec as my trading tool. Is there an easy piece of software or even a technique you'd recommend to work out my tax obligation, and also let's me know easily what i have 'left over' for future tax years. I can probably do a manual process for the fifty or so sells that i did but not sure if the tax office would appreciate that, and will be messy for future year calculations

Thanks in advance!
redskyfire