taxation issue

Hi fellow posters

some free taxation advice sought from any poster with experience and knowledge- assume I wish to hold say IMU (as I do) for at least a year which still in its infancy still to run and not to be classified as a trader-(I hope to acquire further parcels of this share s at different times in the year)- if for reasons of financial need or other unforeseen reason I wish to sell part of my aggregate holdings acquired later in the year ( I hold a non- res visa and may qualify for a non- res discount and live abroad as South African citizen but hope to return to live permanently in Australia.- does the sale automatically relate back to the initial purchase if even if I intend to sell a parcel acquired later in this year?

I know the standard test is to determine how long the particular shares have been but its the date issue in regard to a disposal of some shares that vexes me. and is there a way to make sure my original one year holding remains intact and gets me CGT relief, all things being equal?

I cant find any direct answer to this question in my research. There may be a direct authority on this issue. Any input would be appreciated and it must occur a lot in practice. Thanks. Karrotz