Yes. You need to think if the compared time zone is ahead or behind yours.
The formula is simple, and the sample formula in my last post works. The thing is, you need to think which way you want to do the time zone conversion.
A real life example: I am in time zone UTC +2 now because of the summer time. On a certain website, I work together with someone who lives in Texas, USA. Current summer time (daylight saving as they say in US) time zone for him is UTC -5.
If I want to compare local times for us both, I need to remember that he is 7 hours behind me, and that I am 7 hours ahead of him, and change formula in Excel accordingly. So, the D1 cell in my previous post would be -7 if I compared my time to his, or 7 if I compared his time to mine.
In your case, I think you have done everything correctly but that you have just forgotten that if you want to compare Melbourne time to UTC, it's minus, even if the official time zone there is plus, UTC +10.
This, knowing when you have to use a minus sign even when time zone has a plus sign is important. Always think if source time zone is ahead or behind the time zone you are comparing with.
Reading what I wrote, it really looks complicated
. I really hope you can get my point.
Kari