cap gains tax offset???

have made a nice capital gain on QGC. Bought @ .81 and sold @ ? $5.75. Initial investment in QGC was $20 000. Have held them longer than 12 months so wiil be only disclosing 50%. I have other stock that is in the RED but wanting to hang onto them. There Paper losses would cover most of the 50% Gap Gain if losses were realised. I would like to know how to go about doing this in the interests/approval of the ATO.
I have heard you just cant sell the shares and then buy them back in the same day same price for eg. ATO frowns upon this apparently. What is the standard way of going about this?? Obviously I have 5 months to get this in order.

Regards..Rednoff

p.s. happy to make a gain but I am $40 000 down on another stock but am willing to hold onto for the long term