merge cells based on value of another cell with VBA

I've been working on a project and I'm trying to make things go smoother :)

I have an excel sheet with several columns and as you can see it below, Column A is the importance of the topic(based on information typed in that row) and Column B is whether the information typed is a new information or an update regarding the previous (upper) row. Soo:

if I type "update" on column B, row 3; I want it to automatically merge the cells A2 and A3.

     A      B
1   LOW     new
2   HIGH    new
3          update
4   Low     new
5          update
6          update

I don't know how to write VBA codes but I can mostly understand the codes enough to adopt what I find on internet to what I want to achieve. I have checked so many websites to find whatever I needed but I had no luck so I would really appreciate if you could help me :)