Change background colour to yellow if cell doesn't match the previous cell

Hi, I have a huge table with products as rows and the month Jan-Dec in the columns. Each cell has a price (number).

So each cell is the price for a specific product and a specific month. Each cell is automatically populated by the same value as in the previous left cell. So cell B2 is =A2, C5 is =B5 and so on.

Now the problem is when the prices are changed, it's not very visible in the table, so I wanted to insert a formula that colours the cell yellow when the price is not equal to the month before.

I can manage this cell by cell with the conitional formatting, making a new rule for a specific cell to turn yellow if not equal to the previous cell, but it will take me months to do it cell by cell. There must be a clever formula of function for this, so I can just apply it on the whole table at once?

Thanks in advance

Thank you so much, adding that simple code to the conditional formatting saved me tons of time