Neighbour Refusing Access to The Boundary Wall

Hi All,

The short version,

I live in a new estate in VIC and my garage wall is built on the boundary. I want to put covers on the weep holes to prevent mice from getting in.

There are 4 holes that I need to access from the neighbour's property. But he is refusing to let me in to do that. All I want him to do is to open the side gate for 2 minutes and let me come in 2m into his property to put the covers on the holes.

What are my next steps ?

EDIT 3:
So I figured that they have screwed in the gate post to my garage wall (called the guy who did the fence and confirmed). Texted neighbour nicely again and he does not want to cooperate at all. Called the council about the fence post.

They said although it is illegal they can't do anything and I have to call dispute settlement center and may or may not engage a lawyer.

Both the houses were built by porter davis and mine is on the zero lot line (or supposed to be) - so If I really want to dispute the garden edge, I have to get the boundary surveyed. But if it turned out they screwed up my build and it if is 1mm over, then I am screwed again.

Thank you all for the replies so far, I will wait for a bit to have a think before I do something really stupid, but looks like there is no easy "legal" way out.

EDIT 2:
So I contacted the council, their response was:

It is a civil matter between neoghbours and we can't intervene. They referred me to the dispute settlement center which referred me to legal aid which reffered me to a free legal service which referred me to a site where I can find lawyers that works for a fee.

Proper channels FTW!

Long version.
Until yesterday I thought I had a good relationship with my neighbour. We both built with the same builder and moved in only a few months apart. We used to text / talk and even helped him with a few stuff. I had some mice in my roof and I had a pest controller coming over the weekend. He asked me to cover all the weep holes with weepa covers from bunnings including the ones in the garage wall on the boundary.

Now, my garage wall is built on the boundary (so as his but on the other side - and pretty much all the houses in the estate). I sent a text on Sunday morning asking him if he could let me in for few mins to do that. As I did not get a reply, I knocked on the door in the afternoon and asked again and I was told no. (By I think his dad). They are chinese with not so good english so I thought may be it was just a misunderstanding. So I got one cover and showed him what I need to do and he still refused.

Homeowner was not in, so I gave him a call later hoping that he can explain what is going on. But he flat out refused to let me in. His reason is - "I don't have to give you any reason but I am not letting you in".

There has not been any issues between us except for when he put in a cctv that could see my living room. But he agreed to turn it away and we were fine after that. This was over an year ago.

I am ok to take the legal route if it has to be, but what are my options here ? Thank you.

EDIT:
Thank you for the replies so far. I will ask one more time, but I really think they are well past the point they deserve a nice neighbour. So far I have done these thinking that I'd be a good neighbour.

Spent $500 putting 2 big screening panels to cover my living from his cctv rather than complaining further.
$300 fence extension coz I did not want to see his bedrooms from my living. I did notice that they took away the news paper that were sticked to the windows after this
Did not complain when their landscaper built their garden edge ~50mm into my property
Did not complain when their unmaintained grass invades my front garden beds.

I also spent at least 20 mins trying to reason with people there including the owner and trying to see if I had done any wrong by them.