Plext,
There is no spreadsheet as such. I use a spreadsheet to do the initial CG calculations if I propose to sell any or all of my portfolio. Remember that if you have been dividend reinvesting then each share parcel from a dividend is a seperate share parcel for CG calculation. I then manually pick the parcels that give me the income and CG tax result that is best for me. As this isn't a regular occurrence I haven't done any automation for it. I just apply the ATO rules for allocating the gains and losses, allowing for the 50% CG discount were applicable.
Remember the rules are detailed and if you have shares purchased in the 1990's you also have an indexed option to use when calculating the CG. The indexed method can still be worth using depending on the timing and gains involved. It isn't worth automating as I do it infrequently. It also has to be done twice. Once to decide what will be sold, then again after the sales to allow for the actual prices realised.
Remember that the losses don't have the 50% discount applied to them. They are best allocated to sales which don't have the discount available to use. Any excess is then applied to any indexed gains and only as a last resort applied to gains which have a discount available. For the latter, the loss is subtracted from the un-discounted gain and then the 50% discount is applied. This tends to produce the minimum income tax.